I visited one of our LGS's today and besides buying two near pristine copies of Dungeon 15 and 16 for $.50 each (Sweeeet!!!!!), I got to view Keep on the Shadowfell for an uninterrupted 10 minutes. Now, I didn't read it in-depth, but on first viewing, it seems very impressive. Some thoughts and impressions:
*While I didn't have major problems with the 3.5e delve format, I think that the 4e format is far superior. Instead of splitting the information up into two places, everything is integrated together, keeping the delve's strengths without interrupting readability.
*The format is two booklets, three mini-scale maps, all in a cardboard folder. My only problem with this format is the paperstock. Its more like a flimsy magazine, so durability may be an issue for some groups; the covers also seem like they may tear easier.
*There is a social skill challenge, though it doesn't really use the template previewed in the DMG excerpt.
*There are no new skills presented in the adventure's quick-play rules.
*There are no alignments that we haven't seen.
*The dominate condition allows the attacker to take control of its target for one round. They can only make the target use an at-will power.