There is a marked difference between people with three bars and people with four bars. This has been a problem with COD for a long time and is VERY noticeable.

Here is a common example: I go to shoot someone, will get three or 4 hit markers, enough that they should have died. They turn around and kill me instantly. Watching the kill cam, my gun never fired once.

Or how about seeing someone and knowing you can't do anything right that instant (usually because of reloading) you duck around a wall and move a good three or four feet back only to fall over dead. Watching the kill cam, you see that you never actually went behind the wall, but instead died out in the open.

It is very much worse in this game that it was in MW2.

I thought it might be my connection, but I don't have this type of problem on other games like Halo or Battlefield. On those games I am usually maxed out in the network connection. Doing speed tests, I get about 15 Meg DL, and 2 Meg UL. But unless I am host in MW3, I will be 3 bars. Guaranteed.