I've been studying it for a while. The new Springfield Armory that makes the M1A, which is their own designation for a semi-auto M-14, started out using all USGI parts except the receivers. They did this because there were TONS of GI parts around after the government decided to scrap all the M-14s in inventory by chopping up the receivers so nobody could use them to make evil "assault weapons". Eventually, the GI parts started to run out, and SA started contracting for aftermarket parts and using imported parts, some of which didn't meet USGI specs, and caused quality control issues for a lot of rifles. This seriously damaged Springfield Armory's reputation, and was a major motivation for them adding on a Lifetime Warranty on their guns, promising to fix anything that didn't perform as it was supposed to. Their quality control is back up to where it's supposed to be now, and I haven't heard of any issues with their current production rifles. Their receivers are cast steel, instead of forged and machined like the high-end makers like LRB, but they're properly heat treated, and will probably last as long as an original M-14.
The Chinese receivers were always forged and properly heat treated. They were actually made on US machines that the US Government supplied to Thailand to support their arms industry, and which the Thai government sold to China when they switched from the M-14 to the M-16. Almost all of the parts on the Norinco and Polytech M-14S (for "sporter) are GI spec and interchangeable with USGI parts. About the only things that aren't a drop-in fit or interchangeable are the bolt and the threaded parts of the rear sight.
I've got a Norinco version now, and I've added several GI surplus parts, including a nice walnut stock and heatshielded fiberglass handguard. With the GI trigger parts and magazines, it's got enough compliant parts to add on the GI flash hider with the bayonet lug, without giving the BATFE a fit about turning it into an "evil" rifle. Some of the Chinese bolts were reported to be "soft", or not properly heat treated when these first started to be imported, but I haven't had any problems with mine, so far, and they're still being imported into Canada, apparently without problems with current production.
It's enough fun to shoot, that I just decided I wanted an original, too.