I don't own one, but I have done a lot of "Internet Expert" reading on them. My understanding is that they are a crap shoot as to quality. You might get a good one, maybe a bad one. But everything I understand is that you must use an experienced M14/M1A gunsmith to check them out and assemble them. Some of the tolerences that are out are so close that the "average" gunsmith would have difficulty with making wone function perfectly. But then again, I have read all this off the 'net, not first hand experience.
I've got two rifles built on these receivers. The first one was a Sarco mutt of a rifle built with the Armscorp and a mix of GI and Chinese parts. As it came in, it was unusuable as the sight base was improperly cut. My local service gun guy jury rigged a solution and it is now a reliable and accurate little blaster. He checked headspace and it was fine. The 'smith I used felt that Armscor receivers were usually soft and claimed he had built match rifles which went out of headspace in a few thousand rounds. I don't know if I buy that.
The second rifle is all GI parts and was barreled by a gunsmith then assembled by the gentleman I bought it from. He didn't indicate any trouble at all building the rifle up and the gun shoots just fine. Both are 100% functionally reliable. The only down side is neither of these guns will fit a Chinese pre ban mag (which I have plenty of) while my Springfield receivered gun takes them just fine.
I'll also add that the new Fulton Armory receivers are made by Armscorp but to FA's specs and i'm sure they have had some input into the QC. Fulton is offering a nice deal on their reciever complete with bolt and barrel as I recall, you may want to check out their website.