first things first, if you like COD and MW then you will like this. It seems everyone was expecting some brand new version of the MW saga, it was never Marketed as this and so it isn't. What it is, is a brand new chapter with extra features, improved game play in both the campaign and multiplayer. Campaign story is brutal, its straight to the point (unlike like Black Ops where the story could drag on for a while) Action is instant and the new weapons and their feature (like the dual scope) is a great addition. The graphics and models aren't dated at all and they are improved, BF3 uses a completely different engine and so yes they will be different BF3 will have better points but will lack in areas that MW3 will excel.
Multiplayer has always been the big selling point of MW and COD, the re vamped multiplayer environment is great, true there are few servers issues at the moment but that is to be expected, happens with all new large scale multiplayer games. The new upgrade and improvement system works well and is easy to get the hang of. The new weapons is just what was needed, a nice variety of guns!
I can't see any faults personally, I really enjoy this game and look forward to progressing further with it!