I have a DBoys C8 body I bought last winter. No real fitment issues with it at all except I had to sand the mag well a bit. All high cap mags I tried in it worked (TM, CA, DBoys), and plastic G&P midcap mags worked well too, but all metal low and mid caps were too tight. However, once I got that taken care of, everything worked great without any issues. The finish is a bit rougher than that of the real steel, but I think it looks damn close in terms of finish. That being said, if I could have gotten a hold of a Guarder C8 body, I would have paid the extra for that over the JG just for the better quality.
That being said, there are a lot of reports of problematic older DBoys receivers. But from what I've heard of the newer generations models, they fit up well without any mods required.