Lets start this off by pointing out what WotC went out of their way to point out:
We’ve abandoned the Psionics wizard and the following spells: ego whip, id insinuation, mental barrier, psionic blast, psychic crush, and thought shield.
Yes, that's right, the Psionic Wizard got so much negative feedback that it became the first officially abandoned UA idea. While the Brute and the Lore Wizard might be unofficially dead at this point (as the book they were in consideration for has long since printed), and the Giant Soul was recycled into the Rune Knight (but not abandoned), the Psionic Wizard is kaput, recanted, dead, disavowed and officially discontinued. Which is nuts because the subclass wasn't even particularly egregious save for people mistakenly believing that it was a replacement for the Mystic.
What Is Psionic Power?
As I said before, this is a handy little page-long essay on D&D Psionics for those who aren't familiar with it. Which apparently is a lot of people who look at UA. Of note: The Mystic is also abandoned for being too broad in scope. They have picked a direction for Psionics, which is more or less just putting it into subclasses and feats so all the existing classes can have psionics. Which makes the abandonment of the psionic wizard sting a bit more in retrospect. Also in this section is a Handy Grey Box that says that Psionics are a “sometimes magic”, which sends up a red flag for me immediately. If you are going to have psionic/magic transparency (which you should, because otherwise it ends up badly for typical players and especially places like AL) it better be full tilt.
Psi Knight
The Revenge of the Sith.
Psionic Talent
So basically, it's a superiority die. Functionally, it has a weird curve ball where if you roll max you make the die smaller until you hit a d4, then you stop getting dice if you roll max. Conversely, if you roll min you get a bigger die for next time. I have to say, I don't like it. It's too random, you can actually just blow your load on the first two rounds of a day and be stuck without a subclass for a long time. Then there are the powers that just strait up shrink the die, with no chance to make it bigger. They do include a bonus action mulligan once per day to reset the die, but really that seems more like bandaid on a problem than an actual solution.
Finally, if you have multiple Psionic subclasses and/or the feat, you only get one die (the biggest) for all of them. Tying even more abilities into a single point of failure, and creating a strange situation where you want to take a feat to shore up your class features when you multiclass.
Sure, power points as a universal resource represented by dice can be workable, but this implementation just doesn't gel with me.
Protective Field
A reaction to reduce one source of damage by your die+int. Potentially usable every round, but the buffer is rapidly overwhelmed by monster DPR beyond tier one, and it doesn't carry over to other attacks should you somehow block all of one hit. Even making it a bonus to AC for one attack would be better for long-term sustainability.
Psi-Powered Leap.
You are jumping, like 9', farther than normal. It uses 1' of movement. It's a bit annoying for mapping to a grid, but it can get you out of a pit trap.
Telekinetic Strike
The most likely use for your Psi-Knight's die. It's just extra force damage on a close-range attack.
Telekinetic Adept
A few more mind powers.
Psionic Thrust.
Upgrade to
Telekinetic Strike, now you can knock people around or push them prone.
Telekinetic Movement
On the one hand, it can move an object or creature of any weight. On the other hand, apparently Yoda was fibbing to Luke, because size is the only thing that matters. Either way its handy.
Psi-Enhanced Metabolism
Psionic and poison resistance. Kind of lack luster at level 10. I would have expected something more like force-choke or even a mind-trick.
Bulwark of Force
You can give out half-cover to your party. Once per day is free but other than that it shrinks the die. I like cover and wish it was used more often. But as a level 15 ability? Other classes can fly at this level and you are giving people something that doesn't stack with good positioning and tactics.
Telekinetic Master
Telekinesis the spell. Int is your secondary stat, but at this point you should have at least a decent smattering of it. And along with your naturally proficient con save it should be hard to knock your concentration away. However, it's very late in the game to have a crowd control option.
Thoughts:
It feels less like a paladin this go-round, but somehow it lacks teeth later in the game. Like you could combine the level 10 and 15 powers, throw in a force-choke at level 7, knock telekinesis down to 15, and make the capstone “you don't run out of psionic dice” to shine up the class.
Also, it's still not a psionic warrior, with all their body augmentation and crystals, but I suppose they have abandoned that baggage when they swapped the name.
Soulknife
You shouldn't bring a mind-knife to a mind-gun fight.
Psionic Talent
I still dislike it in general. However Soulknives have less opportunities to grow the die, which makes it kind of suck for them.
Psi-Bolstered Knack
The main way for a Soulknife to grow their die, is to
fail a skill check. Yep, that's a head-scratcher, especially at later levels when Rogues are tops for skill use.
Psychic Whispers
Or I suppose you could try spamming telepathy, but that doesn't seem intentional because you aren't actually doing anything else while you grow a die.
Psychic Blades
The blades are back, no longer do they require a bonus action to summon, and are instead auto-summoned (and de-summoned) when you attack with a free hand. A little less clunky to use over all, though it does prevent you from using Booming Blade with your knife.
Soul Blades
Finally, a combat use for your Psi-Die.
Homing Strikes
So if you miss with your Soulknife, you can get an accuracy boost, but you always shrink a die when you hit when you use the power. Does that mean if you max out your die (and presumably hit because of that) you shrink two die sizes? Bogus.
Psychic Teleportation.
Random distance teleport (which would be ok, if it was a minimum of 10') and again, it doesn't sync with a grid, which is a pain. Also, your die shrinks by one no matter what you roll, leading up to another double shrink!
Psionic Veil
Invisibility, but it recharges when you shrink your die.
At this point, it occurs to me that the fluff for this subclass contains something about having a lot of mind powers but before this point it's just been stabbing, teleportation, telepathy, and being lucky. Where is the telekinesis analog? The Arcane Trickster is shaping up to be a better “psionic” rogue than the Soulknife is so far.
Rend Mind
And the Capstone for the Soulknife is, Stunning Strike, the level 7 monk power. To be fair, it's not much different than the old capstone, but really, that ability blindsided everyone because it was a spell saving throw on a Rogue so everyone had bunches of questions about it.
Thoughts:
The Soulknife got robbed I tell you. They lost a few of their more interesting abilities, and their die has horrible shrinkage problems.
Psionic Soul
Now with 66% less squid flavor.
Psionic Origins
I miss the Abberant Soul's decidedly far-realm (but only if you want it) flavor. It was more interesting than “I dunno, I just I woke up with mind powers yesterday.” By quite a margin. Also, this feels kind of like the Wild Magic Sorcerer, which isn't a good thing.
Psionic Talent
The sorcerer already has a pool of points, it is no surprise that this die mimics some of those effects. However, I have to say that the die feels incredibly forced on the sorcerer for that same reason.
Psionic Discovery.
It's an expanded spell list that can put any level of spell on your list from two different schools. It doesn't even auto-shrink the die. Like what.
Psychic Sorcery
Subtle spell on all your spells without the cost of a Sorcery Point! I suppose the theme is on point, but this is exactly the kinds of shenanigans that should be avoided with psionics. Display less manifestation leads to problems. But besides that, it's a free metamagic, that isn't named metamagic, which means they can stack more metamagics on a spell when they cast it. Also also, it can bypass costly material components! Like wow.
Telepathic Speech
Slightly less useful than the Rogue variation, but hey Soulknives are kind of in a bad spot right now anyway.
Psychic Strike
You can deal extra damage, note that this doesn't add to the spell's damage, it's just floating extra damage to be applied to a creature you hurt. Which makes it less synergistic and more of another free metamagic, but not as good as the other one.
Mind Over Body
This is double dipping, which I don't like despite how many red flags were set by that level 1 power. Otherwise it's a standard level 14 flashy sorcerer mobility power.
Psychic Aura
This is a bit wild, the damage isn't anything significant to be sure, but the fact you can automatically fry anything and everything(even things that you aren't aware of or can't see) that steps near you with the added half-speed rider is kind of crazy for a power that you can use an unlimited number of times per day. I suppose the fact you roll your Psi-die (which lets it shrink) is intended to be the limiter, but the ability to indiscriminately hurt creatures you aren't even aware of is still nuts.
Thoughts:
Ok, maybe the Sorcerer is actually the poster child for why a psionic pool of power doesn't work for every class. I'm mostly sure the only reason the Aberrant Mind got a second pass was because of the people saying “Why is the psion a wizard subclass? It should be a sorcerer subclass instead!” Despite there actually being a psionic sorcerer, and the psionic wizard not actually being a psion...
Ugh... So many good UA ideas sacrificed on the bloody alter of mass feedback.
Spells
They got rid of a bunch of them because of issues. Would have liked to see more fixes than trash binned ideas, but hey, what made it?
Intellect Fortress
It's ok. Tweaked from the last version, it now grants psychic resistance (and a lower spell level) instead of letting someone reroll a save.
Mind Sliver
How many times are we going to get this exact same cantrip? I am willing to bet it's going to be printed at this point, but I am still going to point out it's basically the best combat cantrip in the game right as-is.
Mind Thrust
Significant nerf, now the target can have a move, an action, or a bonus action (but no reaction) when they fail their save. It's still really good though.
Feats
Several of these have a Psi-die prerequisite. Which is kind of a bummer if you just want a bunch of psionic powers without having the subclass.
Metabolic Control
A half feat that lets you short rest faster or not have to eat. Kind of a fluffy thing, and still no psionic self healing as the short rest still takes 60 seconds.
Telekinetic
A half feat that gives you
Mage Hand and lets you push people around with it. Needs you to have a psi-die for some reason. Otherwise I'm still a bit perplexed as to why
Mage Hand still doesn't scale with level.
Telepathic
You can shove your thoughts into someone else's mind or read their thought as the spell. The mind-broadcasting part of the power is particularly weak, as it doesn't auto-translate like most other kinds of telepathy do.
Tower of Iron Will
This is actually really handy, you can add your psi-die to a failed saving throw, which might make it pass. Can even be your friends saving throw.
Wild Talent
The most interesting of the new feats, this one is also a half feat. But it gives you a Psi-die that scales with character level instead of class level, which enables multi-class builds. Also it gives you some minor dice manipulation, but mostly it's just an enabling tool for characters who want to be psionic but not commit to a subclass. Unfortunately it's not particularly good by itself.
Thoughts:
There is a good idea flowing through here, I imagine Dark Sun Characters would automatically start with something like Wild Talent then branch off from there. However there needs to be more options and especially better options for people to grow into.
In conclusion, about the psi-die
It appears as if they are trying to create a feedback loop in the subclasses (and also feats) where you do your basic shtick, and you get a resource, then you spend your resource to do cool and better things. Which is the basic idea of how I would have done it. Imagine a fighter doing a few normal strikes as a combo, then unleashing a finishing move. However, the way they have done it is kind of bonkers because you start out with the max resource pool and it randomly fluctuates in the middle of combat until you just run out randomly (or purposely) I would like to see them try a legit combo system instead, mostly because I think it would work better.