The only thing it really needs is more power points.
Yeah, but it's not like that's unique or cool or anything.
The psiwarrior already has several unique powers it can learn, making it stand from other psionic classes.
And it's a base class very similar to the fighter, which I think is intentionally generic. You can make an archer, a sword and board guy, a tripper, etc. It has to cover lots of "fighting man" archetypes.
The other thing the Psi Warrior could really use is a class specific free (or cost reduced) quicken power effect. I've read a few campaign reports where Psi Warriors had problems compared to martial adepts because they had to spend 2+ rounds buffing at the start of each combat.
If Linked Power is allowed, it goes a long way towards fixing this. Of course, you could just give it to them as a freebie, but with all their bonus feats, it's not really needed.