I like them but hate the mag release and how it pushes out the opposite side, causing mag changes to be hokey. The one I shot I had to strip the mags out on top of that. They didn't drop free. Combine that with the fact that you are stuck with the trigger because several aftermarket companies said it's too complicated to make parts for.
Also, there's some big names that started doing high round count tests and then kind of just stopped and never mentioned them makes me wonder.