I bought 2 or 3 different G400s (can't even remember) and after some time every one of them started to not respond properly: the mouse would'nt respond for some time and I even heard the windows sound of unplugging hardware devices. This phenomenon got worse with time, at the end the mouse would unplug itself for several seconds. There are some people who have the same problem, as I read in the Logitech forums. It seems to be a problem, which is caused by bad manufacturing (maybe this is the reason why it is so cheap). I probably will try to get a refund or atleast a new mouse from Logitech. For now, I just bought a Roccat Kova and it's just really awesome. Actually I'm glad, that the G400 fucked up, because I now feel the Kova is a much better mouse (judged by the overall feeling) anyways.
Just wanted to make sure, that you all are aware, that the G400 is from poor quality and will break after 2,3, or 4 months; so don't buy it!! Although in theory it is a great mouse.