I've been working with AR's for some time now, and DPMS is right in my "back yard". Anything I order from them I could have the next morning. For me, the were quite handy.
DPMS doesn't do any of their own machining, all of it is contracted out. Back several years ago, they had some terrible problems with the quality of machining they were getting. I had so many problems with, both their upper and lower receivers, I quit ordering from them and refused to work with customer lowers if they were DPMS. I talked with the owner, Randy, and he always took care of the problem, but I just couldn't make money with their product.
Now, several years later, one of the dealers in my area started stocking DPMS products, including stripped lower receivers. Let me tell you, in the last 6 months or so, I have had many DPMS receivers through my shop and they have ALL been top-notch. In fact, I was so impressed I called and told their sales manager just that. This weekend I am at a gunshow in St. Paul, MN. and DPMS has a large showing there. I spent over $3000.00 on small parts at their booth!
I have, in the past, worked with the same barrels they are using for their "upper line" rifles. I purchased these both as barrel assemblies from DPMS and barrel blanks from Wilson. What I found was that not all of the barrels were capable of great accuracy. Most would produce accuracy that would make the average AR buyer happy. A couple of the barrels produced accuracy that would make even a fairly discriminating shooter happy.
Bottom line: I think, at this point, DPMS quality is quite good. If you purchase a DPMS rifle with the stainless bull barrel, it will probably be a shooter.