I assume you mean their Pathfinder psionic stuff.
Their races are pathfinder-balanced, the Elan is now playable as a Wilder (which is 10 levels of awesome), the feats are good, and every class got some new tricks.
I've used it in two campaigns, one as a Dm, one as a player. The one I DMed had a Soulknife and a Psion, and both worked quite well. The Soulknife's Mind Blade talents keep them more than relevant, they're more like close-combat damage specialists, while the Psion is still the awesome control/damage class it was in 3.5.
Neither had any significant balance issues, except maybe that the Soulknife is a little too strong compared to most warriors around levels 2-6, but not by much. Personally, I'd have given the Psion class more powers known, as by the end of the campaign the Psion was feeling pretty limited in their abiities (ended as a level 10 Nomad).
I played as a Vitalist for a short 4-session campaign, and it was excellent. The class functions quite well as a healer, a protecter, and a decent damage dealer depending on their powers chosen. Their melee touch attack that steals hit points is incredible, especially with the feat that increases the damage from level + wis to 2xlevel + wis. Their class features are a little underwhelming until you hit 7th level, when the touch attack becomes ranged and you never need to carry a weapon ever again.
For the rest of their stuff, I can't comment on the rest of the classes, though from what I've heard the Psychic Warrior is up there with the Magus as best warrior-mage, with a focus on close-combat damage powers and buffs. The Wilder still has the crippling tiny number of powers known, but Wild Surge is stronger and better, and the class is still very fun. It might not be Tier 1, but nothing's quite like screaming so hard your opponent's brain exploded from the sheer awesome.
All in all, it's worth checking out and using. The Soulknife is a fun alternative to a Fighter in a group, and avoids the tedium of a player who'se always looking for the next infinity+1 sword. I hear the Aegis does the same thing for armor, but I'm not sure.