Umm, what? Psions are very noticeably weaker than Sorcerers and arguably Favored Souls as well.
Weaker in what way?
No auto-scaling on their powers is a big one (compare, for example, Energy Bolt to Lightning Bolt. A Psion pays effectively an 8th level spell for the same effect as a Sorcerer gets from a 3rd). Plus, their best tricks are just "tricks" for a Sorcerer. The most powerful powers in the game are modeled after Sorc/Wizard spells and typically nerfed in some manner.
Add in the lack of general support, and you end up with a weaker class. Plus, metapsionics aren't as powerful as metamagic due to the requirement of your psionic focus on each feat, as well as power points that could have gone into augmentation.
never mind that any power selections you make are permanant (unless you're smart and grab Psychic Reformation), so you had better pick well and ration your PP well.
Ever grab ten power stones and "learn" spells off of them
Doesn't work that well, since any use of a power stone (even if manifested from your own PP) flushes the stone.