I don't know what they did... I got it at release and it was probably 90%. The only issue was occasional stuttering during matches. Now though, I have constant lock ups or loss of connection.
I had been hitting ctrl+alt+del and closing the process when it freezes but let it go last night and it just hangs for about 3-4 minutes and finally unfreezes and I was still in the game.
does suck to lose challenges when you prestige. I'm on prestige 3 and don't think Im doing it again.