I'm mostly familier with 3/3.5 editions of psionics, but my understanding was that they were overly powerful in the previous edions. In 3rd they seemed very weak to me, but that was primarily because I would take blasting over other spells and they sucked at blasting.
3.5 psionics are leaps and bounds above 3rd. The dropped psionic combat, and allowed for augmentation. Some might consider them overpwered, but one thing for sure is that they are better than wizards at blasting, at least until they run out of juice. This is with out metamagic feats though. Then it would come down to Energy Missle/Stun versus Scorching Ray and the orb spells. Psionics suck at buffs, all they have is self-buffs, fine for a gish but lackluster anything else. How ever beating people telekineticly with a dead goblin at 3rd level is just plain awsome.
Incarnum seems very intresting to say the least. With how they have all their abilities for the day up all the time, but only enough power for a couple of them to be fully powered. I also like how what I consider the primary incarnum class the, Incarnate. Your Neutral on an axis and non-neutral on another, and you get abilities based on your alingment. So you can be Evil Incarnate

Warlocks are the opposite end of the spectrum from having more damaging abilities that can be used less than wizards, they go for crap damage that can be used infinitely. I played a warlock in a friends campain and was decent. It was a lot weaker than my previos characters in that campain. On the offense, but it had a bunch of usefull abilities that I really didn't take full advantage of.
Artifacers from my understanding are extremly powerful if you go full-blasting, but the time I played one I was going for a mediocre fighter with jacked up equipment so it was a little lack luster. But the fact that they know all their infusions and one of their infusions allows them to duplicate other spells was cool. I used it to cast mount a halfdozen times to help move a bunch of refugees.
Unearthed arcana has spells that any body can do, but they take a indeterminite amount of time, allows for the cultists that arent the BBEG to help with the spell of doom I would imagine.
It also has spell points and casting spells with recharge time. I like both things to a degree, but I have no experience with either of them.
Considering Spell Theif a varient magic system might be strecthing it a little bit, but they seem intresting, but very campain dependent. The ability jack spells and junk off your enemies would be awsome in the right campain.