I found the sales pattern interesting for D&D 4. The early folks picked up gift sets in the first three or four days of release. About half of those pre-ordered and saved some money with us. The first 10 days also saw lots of Player's Handbook sales, as potential players and unsure game masters wanted to check it out before committing further. We're selling a steady 3-4 PHB's a day right now. After the first week, we're now slowly seeing those early PHB buyers return for the Monster Manual and Dungeon Master's Guide.
Sales are sluggish of these supplement books. We'll likely see a much slower sell through of these than in previous editions. I call them supplements because the PHB is really D&D 4 self contained, a great bargain, a weight saver, but I think it will relegate the other two core books from core to supplements. You don't need a DMG to play the game; it has no significant rules content for a game session. You only need a monster manual if you want to build your own adventures or use third party adventures (not available yet). I think WOTC broke their own marketing model here, but it benefits the players, so all is good.
Reviews so far have been very positive. Early PDF downloads created a lot of excitement. Buzz from web forums and podcasts have been strong. The 2d6 feet podcast had a long D&D 4 analysis which I recommend listening to. It's one of the only podcasts I attempt to listen to regularly, although I'm usually a few months behind. World D&D Day at both our store and Endgame was packed, as people came to try out the new 4th edition. Packed means 5-6 tables of games going throughout the day. All gaming buzz is local, and I know there are rust-belt stores that have seen a lot of player resistance, mostly for economic reasons. One interesting dissenter in all this is Chris Pramas of Green Ronin games. His blog has been fairly negative about 4E from day one, but he has lots of good analysis of why. I don't usually agree, but that's mostly why I read it.