Was thinking of building a another AR, flat top carbine, but using all DPMS parts, Lower, Upper, etc...

Is there any issues with DPMS as far as Quality, Fit, and Function of their parts?

Thanks for any help anyone can provide.

I built (my friend built for me) one about a month ago, the parts went together easily and the fit was tight and well matched. It was the AP4 flat-top carbine and I am very happy with it, a great shooter. I havent actually been able to check MOA yet due to various reasons, mainly I am a bad shot but I will give it a try when I hook up my bipod.
(FYI) Honestly I bought a kit because I thought I was going to save money but there wasn't too much of a savings at all.

My DPMS AP4 upper fit well with RRA lower.  My LPK was also DPMS.  Haven't encountered any problem yet.

I bought a dpms kit and put it together, still haven't even put a hundred rounds through it yet, but it shoots very well so far, the fit and finish are immaculate, and I couldn't be happier.  THe only problem I encountered was that the hammer spring was too weak, but I bent it with pliers a little and now it works fine.