Regrets? I have a few...but then again, too few too mention.
Ah, who the hell am I kidding? I love to whinge:
THE SPLATS
Wizards did an excellent of upholding the dedication to poor quality that TSR gave us with the kit-splats of yesteryear. Six pages of errata on Sword & Shaft alone. Quite the accomplishment. I liked some of the ranger-oriented PrC's from Master of the Wild. That's about it.
Deities & Demigods
Completely and utterly pointless book. Not only is there no thought to put some material in here that might in some way actually be useful prior to epic levels, but it's not even useful
at epic levels because they went and published the damn thing a month before the Epic Level Handbook. It's a bit much to accept that there are mortals who are more accomplished warriors, more knowledgable masters of magic,
and more divinely-powered clerics(!!!) than the gods, who stop at 20th level in any class.
Urban Arcana
It's not an altogether bad book, but it didn't seem to occur to the designers that they needed to offer up something other than a retread of kobold-bashing, chest-looting, fireball-tossing D&D in a modern setting, replete with magic items, monsters, spells, organizations, et al reworked as possible to give them a modern coating of paint (e.g. "demonic armor" becomes "demonic leather jacket").
Creature Collection II
Got this book for a discount at DragonCon for the birthday of a fellow DM, and found out I'd gotten his birthday off by an almost perfect six months off. I thought I might get at least some use out of it, but in typical White Wolf fashion it's all fluff and flavorful monsters that might be all surreal and gross and horrifying and so forth, but designed without any thought of making them interesting or original opponents in a tactical sense.
The Longest Night
This tops the list of my all-time regrets. Hate to say it, but my faith in ENWorld's reviews dropped sharply after I read through this highly-touted book. Like Creature Collection, it's full of creepy ambience, but little meat and very, very little respect for players. Heck, make that none.
SPOILER ALERT! Mainly, the players fight zombie after zombie (but called "thralls" in order to cleverly disguise what they are as something completely original), and are shuffled like cattle from one encounter to the next. If the players are supposed to get trapped according to the script, then they're trapped. No way around it no matter what they do. If they figure who the not-so-cleverly-concealed mystery villain is (which they can do if they so much as catch a glance of the book's cover), jump'er on sight, tie'er up and stuff a sock in her mouth and sit on'er, the script says the villain still gets away the second the players heads are turned (if their heads don't turn of their own volition, you have to tell them their heads turned at some point because they just had to). If they sneak up the bad guy and try to drop barrels of naptha on her, the script says she immediately casts a featherfall on them, without regard to surprise rounds or initiative. And worst of all, the script depicts the climax of this adventure as a combat between two NPC's whose power levels vastly overshadow the players. They're expected to just sit back and listen to boxed text until their cue for the coda. Lame and unacceptable.