3.5 just created more problems than it fixed. I can point to Complete Arcane, Complete Divine, and Expanded Psionics Handbook as being pretty serious offenders. About the only thing less broken about 3.5 is that there's so many munchkin additions and changes, that everybody can play a different kind of munchkin PC and the DM will still have munchkin NPC concepts left to spare for use as villains. Then of course it's all about winning initiative, to determine which side (PCs or NPCs) gets obliterated first in combat. 3.5 rewards powergaming more than 3.0 did, which leads to less-munchkin or less-experienced players feeling useless in the party. And frustrates DMs sometimes when PCs pull cheesy combos that the DMs didn't anticipate or know the potency of. Much less likely in my experience with 3.0 (but I'm certainly not saying 3.0 didn't have a few broken pieces in many of its books; it did; MotW especially never struck me as having any real, rational thought put into it).
And besides, plenty of 3.5 changes came about without any real need or purpose at all, just there to make it feel like more of a significant revision, needlessly confusing matters for many DMs and players who had used 3.0 before.