I mashed mw3 all day today, there was some stupid stuff going on. Hand guns over powering LMG's, people getting shot through buildings, people under the map running around killing everyone and not getting a single death, the worst one and the most frustrating one is the hit marker issues. Several times today I've seen or I have emptied a full clip into them or got a definite head shot only for the other player to shoot / stab me. On the replay it shows me just stood there not even firing my weapon or I am doing something retarded like shooting the floor.
This game will be awesome when they sort a patch out, they need to do it now IMO