1: People don't see the rule that you can only use up to your ML in power points at once and think Psionics can nova too easily.
2: People don't see the rule that you can only use up to your ML in power points at once and think Psionics can nova too easily.
3: People don't see the rule that you can only use up to your ML in power points at once and think Psionics can nova too easily.
4: Psionics have a really, really shitty design history. This includes the 3.0 version that's the biggest change fom 3.0 to 3.5. Naturally this legacy has soured opinons.
On the opposite end, things that are genuine problems
1: Plenty of things that were bad in the sense that they suck. Soul Knife was basicly useless, and the book gave the exotic race tax to its new races even though they didn't deserve it.
2: Support was extremely scattered, putting Psionics in that pale twilight where it was neither a self contained system, nor a well supported one. Since Complete Psionics doesn't exist, just a few random previews on WotC's website, you've got the (largely excellent) web articles, Secrets of Sarlona (which is not only setting speciffic, but covers a part of that setting few campaigns touch), and some random powers and feats in random books (most of which was just psionic versions of magic stuff) with no real rhyme or reason.