Main issue for me is the spawns, but the last few cods have had a horrible spawn system (mw2 being the best game for spawns yet imo) if they could mimic mw2 spawns even partially this would make for a very fun cod game
bad spawns just make the game so much harder to enjoy when you press x and get hit by a grenade or bullets within a second or 2
as for the maps, it's just a learning curve.. everybody hates the maps in a new game for the first week or so