Well, after four "Complete" books from WotC and no telling how many similar products from secondary and tertiary vendors, I've concluded the core character classes from the PHB and the prestige classes from the DMG are all you really need. I haven't seen one brilliant class idea that tempts me to redesign my characters' progressions through 15th level or so -- and by then we're ready to move on to a new campaign anyway. At most, all the class tweaking needed can be done with a few well-chosen feats. The rest is Complete Fluff.