Chun-tzu said:
YMMV, but for a combat character, I can't imagine any other first level spell/psi-power I'd rather have unlimited use of than healing (even if it's primarily between fights).
It's not a question of whether it's useful. It's a question of whether it's useful enough to lose a level of Psychic Warrior (with their own spell progression, higher HP and BAB, 1/3 of a Feat...) On the other hand, being a Psion gives a psicrystal.
Let's say I have an 11th-level Psychic Warrior. That gives me a grand total of 40 power points. So, if I use my ENTIRE power pool, I can heal 140 hit points. With a CON of 16, at that level I'd have 86 HP, so between fights I can heal myself almost two times over, IF I blow all my power points on that. If I use half of my power points for other things, I can only heal 70 HP.
I didn't even include enhancement bonuses to CON from an item or Animal Affinity. Let's say +4, bringing my total HP up to 108.
(Actually, my character is a Ranger 1/Monk 1/Psychic Warrior 7/Diamond Warrior 6, but who's counting? She casts as an 11th-level Psychic Warrior, and that's what we're discussing here.)
The biggest problem is that the healing ratio is only 3.5:1. With the really small power pool of a PsyWarrior, this is crippling. At this point I'm not even looking at between-fight healing, I'm talking about day-off healing, where you wait until the next day to heal yourself. A Psychic Warrior who saves all of his points up for self-healing is just an underpowered Fighter/Rogue.
Now, the alternative:
Vigor ((3*level, max 18) temporary HP for 1 power point) or its upgrades can be REALLY powerful. Since they only take 1 action to cast, they become really useful to cast during combat with a haste action.
Inertial Barrier (DR 10/+5, (10*level max 150) points absorbed for 7 pp) is even more efficient.
The point is, throw on those, a Displacement, a couple Animal Affinities, and maybe a Polymorph Self, and you're far better off than if you saved your power points for the self-healing.
That's not even including Deep Impact (5 points per use) or Psionic Weapon (1 per).