Only ones I've fired are Bushmaster, DPMS, and Colt. They all worked fine. As for build quality, Bushy, Colt, RRA, Stag, Armalite, CMMG, etc are all good. Haven't picked up an LMT but they have a good reputation as well.
My advice with ARs is: see what you are willing to pay for, and go with the rifle that has the features you want/need at that price.