The drow book looks decent on first blush, although I'm worried it's going to stay too close to the traditional canon. Not all drow worship Lolth -- heck, the very first ones ever to appear in AD&D didn't! -- and the spider stuff could frankly use a break. That said, what I saw in the preview does look good. So that's a definite maybe.
Both the Sinister Spire and (surprisingly) Expedition to Undermountain seem like possible buys for me, since both seem like a good fit for Ptolus. Heck, if most of Undermountain is just a level 1-10 dungeon under the streets of a city, that all but screams out for slotting under Ptolus. Hopefully it'll get better editing than the latest Expedition to hit the streets. That's likely to be my deciding factor.
