The biggest thing I've seen with DPMS is their QC or lack thereof. At the LE agency where I am employed, we are issued DPMS rifles. I am one of the armorers for those rifles. None of the castle nuts on our rifles are staked, some of the gas keys are and some are not. It also not uncommon to have quad rails spin loose on the range. My rifle in particular is a 2004 model, and the only issue I've had was the castle nut which allowed my stock to spin free on the range. Otherwise, yes, it has been a decent rifle. But I still wouldn't pay over $600 for one.
I paid $1000 for my last Daniel Defense rifle... That was money much better spent.