My thing with Psionics is very simple. I don't see it as something that fits into a fantasy setting. To my addled way of thinking, Psi Powers belong in a modern or futuristic setting, rather than along side Wizards and Clerics.

Mechanically, the rules are fine, though a lack of fluff in the SRD is annoying. For me, it's more an issue of style and theme over the rules say I can.