Speed! Operating pressure, accuracey, and the feel!
Trigger loosens on mine, nothing else.
I love this gun. I had a lot of problems with it my first few games but i just have to brake it in. It's really fast, it has a nice trigger but i'd get a new one just so that it looks more pro. The trigger is very adjustable but it loosens after a while. It's pretty easy to disasemble and maintain. You almost never chop paint when your eyes are on, but if you do, everything messes up. My ball detents got stuck and some paint got in the bolt so it wouldnt work right. But i fixed it up pretty quick and it was shooting great again.
If your thinking about getting this gun, GET IT! It's so worth your money! I'd probobly spend $400 on it if it was that much. It wouldnt be that much of a rip off even at $600