Well I'm gonna give a quick review from what time I've played it. I picked it up at midnight last night and I must say if you are used to the noob friendliness of MW2 you're going to be disappointed in this game. Therefore as of right now its better than MW2. Now I'm only commenting on the Multiplayer since I haven't touched the campaign yet but I will do so soon. Here are the things that set it apart from MW2 MP wise.
1. Recoil, Recoil, Recoil. Obviously I haven't tried every gun out, or even 1/2 the guns but out of the 5 or 6 guns I've used so far there is much more recoil. If it stays like this then gone are the days of shooting people from the across the map with ARs that are more accurate than a sniper rifle.
2. No more stopping power. This right here makes the game much more rounded and better. No stopping power therefore the other perks are worth that much more. You also feel the weight of the guns now so I'm finding myself using lightweight with the AR because it seems my guy runs that much slower than with a SMG. I never was a lightweight guy because I just felt guys moved fast enough in MW2, but in this game Treyarch has tried their best to make the perks worth something.
3. Better maps. I think I've played every map but 1 and I must say they are more balanced and there isn't one map I don't like. Nuketown is possibly my least favorite and it borders on not very good but still much better than MW2 when I hated half the maps from the start and learned to tolerate them.
The game just feels different. Way different than MW2. You can definately tell this is not Infinity Ward when you start playing this game. SMGs are useful now, ARs aren't as overpowered, and best of all NO QUICKSCOPING. I haven't tried the LMGs that much but this game just seems so much more balanced and put together. Graphically as good as MW2 IMO, possibly better.