I don't think I've ever had a failure with Bushies .. wait, yes. I did have an old 16-incher fail consistently on one mag, but it was the mag that was pooched -- the mag latch hole was cut too high in the body, and didn't get the round up high enough for the bolt to consistently grab it.
I'm not swayed on the plastic ARs.. possible reliability issues aside (and never having owned one, I couldn't say) I'm not sold on the weight savings. Pick up a stripped AR receiver sometime -- it's already superlight in aluminum. Most of the weight in an AR comes from the barrel and all the gizmos, far as I can tell.
Personally though, when I get around to getting an AR again, it'll prolly be a Rock River -- both work just dandy, but the finish and trigger on the RRAs I've seen has been better on average than the Bushies. That could be a sample size issue though.