A lot of people seem to not be factoring in the impact maps have in FPS games. It's not just, "oh it's just a new map pack". The maps in MW3 would have never been in MW2, ever. In fact one of the main focuses on MW3 was based around the maps. Not saying the maps are necessarily good, but they're really a lot different than MW2 and Black Ops, although some are similar to CoD4. Similar as they may be, the maps in MW3 are designed in a way that hasn't been done before as far as I can tell. There's not many places where you can camp and be there for more than a few kills. You definitely still can camp, and there's a lot of it at least right now, but you need the whole team or at least a few people backing you up if you want to be successful.
The kill streak system is much different too. It doesn't just reward kills, or kill streaks. It rewards you for playing the objective and shooting down air support. It also gives you rewards just for getting the amount of kills you need in order to get the killstreak in the "support" class. I've heard a lot of complaints about this, but I'm not one of the people complaining. The support killstreaks pretty much discourage camping, because now you don't have to. Sure, lesser skilled players are going to be able to get some powerful killstreak rewards, but if they're going 15-25 to get them... that's not really helping their team win.
The guns also are a lot different than MW2. They all have more recoil, for starters. The Sub Machines aren't snipers anymore. Shotguns are no longer secondary and they've weakened them. In general there just seems to be more gun skill than in MW2.
Overall, MW3 is a completely new experience. A lot of the gameplay mechanics are the same, and I say bravo to that. Why try and fix something that isn't broken? Just to create something arbitrarily "new" or "revolutionary"? CoD4 was revolutionary, don't think they can ever top that game. The problems with MW2 that I and most people have aren't in MW3. That in itself is the only "improvement" needed. Don't really understand what you guys were expecting with MW3. Why would a sequel be so "revolutionary", "new", etc? They weren't attempting to recreate FPS's, they weren't trying to create another masterpiece like CoD4, that wasn't their goal. The goal was to make a more balanced MW2 game. With new features, more gun skill, less camping, redesigning maps, more balanced air support/kill streaks, etc.
Mission accomplished, haters gonna hate.