I played a one-on-one (+ bots) with this guy on London server yesterday.
He's only good in open maps. I've also asked myself if he would not be cheating....
Nevertheless one thing that I find strange (but that might vary from player to player) is that it seems that he is constantly down-pressing the "fire" button without letting it go, as the rate of the shots is extremely precise to the weapon's timeout..
But once again, it's hard to tell if he's cheating or not