FWIW, I took a close look at a Wilson AR out at our local range, the other day, and the receiver was a Rock River. I'd probably prefer a chrome-lined barrel, but that ltd. edition special does look great. (I'd probably also prefer an A2 stock).
As far as I know, Bushmaster only offers a one-year warranty.
As to the comment about Glock's warranty, my experiences with Glock's Warranty Service Dept. have been outstanding, as have the experiences of a couple of friends. I was particularly impressed at the service that I got from Glock, when I blew up my G21, using an aftermarket barrel and other aftermarket parts. The Kb was clearly my fault, but they really took care of me! It'd be interesting to see how some of Glock's competitors would have treated me under the same circumstances.