I checked "mixed bag." 3.x was a tremendous improvement over the quite outdated 1e/2e mechanics, and I really enjoyed playing at levels 3-8. Of course, OGL produced a lot of junk, but there was some very good material as well that much more accessible because of the familiar d20 base.
But DM prep time could be nightmarish and - at high levels - it would take my PCs 30-45 minutes to organize all the buff spells that they cast before battle. Also, while it was tremendously flexible in theory, many of the choices were "false choices" that may have accurately simulated an idea, but left the player with a character that was too weak to participate in the game. Furthermore, in my experience it required a grid to play complicated battles, but it still left the players with comparatively few interesting choices that related to the grid, mostly because "stand still and hack away" was such a dominant strategy.
-KS