Owned one shortly after they were released. Mine was in 9mm and took Glock mags.
Hitting a 20 inch gong at 200 meters was extremely easy with it. Never put it on paper, so can't give any real accuracy figures.
Within 200 rounds, the extractor wore out. Called the company and they offered to fix it for me, or send me 2 extractors for free. I took the extractors, replaced it, and sold the gun.
I really liked to gun, but that one problem scared me off from it. At the time, I hadn't heard of anyone else having that problem, nor have I heard of it since. I WOULD own another.
It accepts standard AR butt stocks, ar pistol grips, and the fire control parts are standard ar stuff. Everything else is proprietary.
ETA: The one complaint I have with it, is you need tools to field strip and clean it. This annoyed me greatly, but still wasn't a deal breaker, and wouldn't keep me from buying another.