Oh jeebuz, one of them.....
I have personally seen 3 of them die mid ride now. Last one was my boss, he cooked the engine 50km from anywhere, and the only good thing about it, was pulling him out of there on the back of the bike he had relentlessly pulled the piss out of for 6 solid months. Keep a close eye on your service times, but I have heard that slow trail riding has killed more 300exc's than thrashing the guts out of them. Its the heat build up in the clutch apparently