Yes, I have one. I haven't had any issues with it so far. The only thing that is really pissing me off to the extreme ("fuck it, I just wanna sell it" kind of pissed off) is a railed handguard that will fit around the piston tube. I've wasted about $450 now trying to make a rail system work. I bought a Daniel Defense Omega which I found wasn't going to fit right out of the box even with some modification. Then I got a Troy MRF-DI. I had it working, but it was still a little tight and slightly off-center. So I pulled the Dremel back out and tried to correct it. I blew a nice hole right through the side of it then threw it in the garbage.
I would say just buy a regular gas gun. You can buy two for the price of the piston gun.