The probem is QC and QA. If you're lucky enough to find a good one, wonderful. That's great, enjoy the rifle. But, they're known to use sub-standard manufacturing techniques and materials, meaning the rifles don't follow the established military specifications. You will be told that DPMS guns are fielded abroad by our military, this is a load of crap. Never have they been, and until they change their practices, never will they be.
Their customer service is apparently a nightmare, I didn't attempt it when I was dumb enough to buy a DPMS gun years ago, and it failed me miserably. I simply repaired the failure and returned the gun to the shop. They've since stopped dealing in DPMS because of how many issues they saw.
For what it's worth, I'd advise you to just buy a PSA rifle/carbine, and then be happy with a quality firearm. Don't play with DPMS, Bushmaster, Olympic, etc.
Now, I won't tell you that my rifle is the best in the world (I paid $1457.75 total for it, shipping and tools included). That would be lying. It lacks some ambidextrous features. It is not a full-billet upper and lower, which some may argue is degrading my accuracy. But the components are mil-spec, and come from manufacturers with good reputations. The gun had one double-feed, due to a magazine which wasn't fully seated. Operator error, the gun had no fault in it.
I trust my rifle, knowing it was assembled to mil-spec, above anything less (to include Bushmaster, DPMS, Oly, RRA, etc.). I'd stand my gun next to any Colt 6920, or BCM carbine, or PSA gun, and I maintain mine is equal in quality.
Do I sit on some pedestal, holding in disdain other weapons for personal reasons? No. A DPMS/Bushy/RRA/Oly gun doesn't meet my standards (mil-spec, QA, CS, QC). I prefer my rifle, personally, over most others because it is more ergonomic for a left-handed person. If DPMS, Oly, RRA, and Bushy all started meeting mil-spec standards, and provided the levels of QA, QC and CS I expect from the manufacturer of a weapon I bet my life on when I go to bed each night, I might own a DPMS/Oly/RRA/Bushy. They don't do those things. So I don't use them.
I don't see this as snobbery. And frankly, if I'm betting my life that the weapon is gonna work if some thug(s) come into my home, I have every right to maintain stringent standards.