Unearthed Arcana IS the Psionic system, basically.
UA powers things up, but it's very very subtle...you shouldn't even have to re-tailor encounters...basically it does it in these ways:
Way A: # of High Level Spells
Basically, you can cast your highest level spells more often under the UA Spell Point system. This means that your lower-level spells more rarely get used, and your higher-level spells get used more often...you as a DM can't prepare for that 'only one Wish per day' thing, because they may be able to cast it two or three times, if they need to, when they get it. This is a minor power-up, since most encounters are based around the capability of spellcasters, rather than the number of spells -- by the time a character can cast Limited Wish, all the critters of that CR take that Limited Wish into account, so it doesn't so much matter how much they can cast it. However this does mean that the spellcaster could blow through one or two encounters, and then be reduced to thunking things with a quarterstaff for the next three hours, too....and if you included a 'boss' encounter, that could throw things for a loop. But it's just something you need to be aware of, rather than balance against -- just make sure your PC's know that lower level spells still have their use, and drain the lower level resources before you dip into their high stuff, to make sure they can't use their high stuff very often (if you start with a small encounter, the spellcaster will likely cast a spell or two for fun, and that means less major spellcasting later on).
Way B: Versatility
1) Everyone casts spells spontaneously
2) Characters who used to 'prepare' spells now just choose a list of 'spells known' for the day, equal to how many they used to prepare.
3) This gives prepared casters a smidgen more versatility -- they can now prepare Fireball and cast it as many times as they want.
4) Because of this added versatility, spontaneous spellcasters are recommended to be given +1 spell/day, for each level except their highest (just a free spell, not bonus spell points). You could inject flavor here, using things similar to the arcane domains for these extra spells.
5) This increases their power slightly. Like with above, it's not something that's gonna throw off balance, but it's something you need to be aware of...your sorc does have an extra Magic Missle to toss around, if they feel like it, now. It's harder to drain their low-level resources because they have more of them. Not significantly more (one MM isn't going to sway the tide of battle at fourth level), but more.
So, really, unless you're obsessive about balance, the UA system is a beaut.
And if you're obsessive about balance, I'd recommend sticking with the slots, since it's easier to balance them.
