I hang around a bit on the HQ games. MOBeach is my favourite server right now.
Version is 1.2 by now, BTW
The cheat I witnessed was either a room full of observers helping one guy out, or some kind of a tracking devise. The guy shot enemies through bushes and so on, - totally while unseeable.
His kill rate was like a 100 to 1 or so, and finally I think he got kicked.