Keep on the Shadowfell has performed its intended purpose: I'm excited about 4e again.
The adventure looks pretty good, but I'm no particular judge of that. It does have a couple of neat miniature (read: whatever weird junk happens to be within reach) placement tricks, which I should have been using already, but at least it didn't take me any longer to find out about them. Just stuff like not putting all the miniatures down at the same time, if a couple members of the group are hiding, or putting the battle map out and letting the PCs move around a bit before starting things up.
If 4e ends up becoming my game of choice (Not that I have one now; I've played more 3.5 than anything, but when I run games, I always have to figure out whether I want to use Iron Heroes or d20 Modern or GURPS or whatever else.) I'll probably get a fair amount of use out of it, because it's got everything I need to start up a game with new players at short notice. I've done that kind of thing before, but this looks like it'll make it a lot easier.
Oh, and there's a gnome in it. Page 31. I guess Mearls and Cordell wanted to let it be known that they haven't forgotten about them. I'll be surprised if there isn't a full gnome write up in the PHB II.
There's not a whole lot more than I can say about the adventure, and the game it represents, without playing it. I'm running a campaign this summer using 4e, and I'll probably use Keep to kick it off, so there'll probably be lots of commentary on it and the system in the coming weeks.