The difficult thing here is; there are obvious cheaters and there are 'hidden' cheaters. Now, the obvious ones are there to ruin your game, like killing everyone with a push on the button. The 'hidden' ones are harder to track down as they are not obviously cheating but rather stay on the background not racking up scores. They're using the hacks more as an extra aid in the game. If think there are more of these type of cheaters than we think.
Other than that, i've only ran into one obvious hacker/cheater so far in 60 hours gametime.