I wouldn't say high round count yet, but I've put through approximately 2500-3000 rounds. Only issues I've had have been that the screw that holds the barrel sleeve on came out and was lost at the range.
I've only had 3 jams and I believe thats because of 1 specific mag from what I can tell, I've got it marked now to see when it happens again.
my only complaint would be the trigger on them, but meh, its a range toy