Sorry to disagree with your first post here, but the UMP is far from broken. To quote Blame Truth: "The UMP isn't broken. At long range, it loses to Assault Rifles, and at close range, it loses to Assault Rifle users carrying Shotgun secondaries."
It's an extremely versatile gun, and in the hands of a good player, it slays little baby buffalo with no trouble whatsoever. The only reason people complain about it is because so many people use it. But honestly, it just makes the game so much easier for me. It's so easy to shut down most UMP users it's not even funny.
Play a game of Domination where your entire team sucks balls and gets you spawntrapped for the entire 10 minutes and then don't blame your team because you didn't do well. In Search or TDM, it's easy to go positive, if not win the entire game by yourself.
Welcome to the MW2 thread!