I haven't heard anything bad. I believe the G27Gen4 recoil spring is the same design as the G27 Gen3 (unlike the G22 and G23) so it should be proven by now. A few other things have changed like the multiple back straps and reversible safety but I haven't heard of reliability issues. I have a G27 Gen 3, a G23Gen4 and a G22 Gen 2 - all have been reliable.
Most of the Gen4 complaints have been about the 9mm.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
US Army 1966-69, VFW Life Member, Retired Geek
Last edited by Quentin; 08-25-2013 at 06:22 AM.