Several of my friends have them with NO complaints. I recently built an M4 variant for a shooting buddy on a DPMS reciever with no problems and the gun runs great! If I build another one, I would not hesitate to get another DPMS reciever or lower.
They are fairly new on the block compared to other AR makers They got their start in the 90's The AR's Ive seen from them are great and they were the ones who had different color handguards from pink, they also had all white funiture on one of their line and they called it the arctic cat. I built a rifle with their lower parts kit on an Olympic arms lower reciever and I lost count of how many rounds I put through that.
Oh if you head over to AR-15.com they have comparisons to other ARs there. The only problem is they don't have every manufacturer of AR-15's listed. A good Ar for the money is Olympic arms I built two of their rifles with no complaints. Also another Brand I've worked with extensively is Bushmaster, and the only ones better than Bushmaster is Armalite, but they want way too much money for them.