I've heard stories of them being hit and miss. There seem to be more people who are thrilled with theirs compared to the people who got a POS plinker in their MP15-22 though.
If you have an AR15 already I would go with a dedicated 22lr upper rather than a 22lr AR that is not really an AR, personal opinion of course, and YMMV.
If you have an AR15 already I would go with a dedicated 22lr upper rather than a 22lr AR that is not really an AR, personal opinion of course, and YMMV.