I seem to be one of the few that sees nothing inadequate about the SOCOM 16, I honestly believe that it's one of the best all around rifles I've ever owned.
Quality control? Well I'm sure that none of us are actually qualified to say whether it's any better or worse than it's ever been, it would take a lot of data to prove that one way or another. I do know that of the three rifles I own two have worked flawlessly and the third had a problem with magazine retention which took about 20 minutes with a file to fix.
I use my SOCOM 16 for hunting and target shooting out to 400 yards just as accurately as my heavily modified Loaded model, that short barrel doesn't make any difference in accuracy but it obviously effects a reduction in max muzzle velocity so you get your best overall performance with bullets of no more than 150 grains but I also have a very accurate 168gr handload that I use for deer and elk.
The biggest issue with the SOCOM is that most people aren't knowledgeable about the strengths and weaknesses of the design. The rifle was built for close quarter combat so it's not well suited for anything else, but you can modify it to make it suitable for just about any kind of use. With the right parts and handloaded ammo it's every bit as good a shooter out to 800 yards as any other rifle. The iron sights are designed for fast shots at two legged targets under 100 yards so naturally they don't work well for accuracy but that's easy to change if you want to (I did, I replaced them with standard sights and they work perfectly). I also added a rail and a Nikon variable scope in a Scout style position (over the barrel rather than over the receiver). The best scope mounts come from a hand full of manufacturers; Sadlak, Bassett, M14CA, ARMS, and Ultimak are the only ones I trust. They all have their quirks and depending on the quality of the receiver you might have fitment issues but they are usually easily taken care of with simple hand tools and a little research.
The short barrel also makes it difficult to find factory ammunition that works well off the shelf. Most commercial ammunition is developed for .308 caliber rifles with at least a 20 inch barrel, the powders used are just too slow for a short barrel, that's why so many people prefer the 18" Scout rifle, the longer barrel works fairly well with the standard commercial ammo. The best off-the-shelf ammo for general use in the SOCOM is any ammo that is equivalent to the military MK319 130gr ammo built for the SCAR. My favorite commercial ammo was the 110gr TAP ammo built by Hornady. I settled on my own version using the Hornady 110gr VMax bullet which pushes 3000 fps out of my SOCOM and I get sub-MOA performance at 100 yards from a bench position.
The stock has always been the weakest part of the accuracy equation for the M1A rifles, the stocks were usually pretty loose and accuracy suffered accordingly. I haven't used the new SOCOM 16 CQB so I can't say if the stock fits well but I suspect it's better than their previous stocks. I have tried several stocks over the years including some pretty expensive models but the best stock I've found for field use is the AG Composites Carbon Fiber CBR stock. It's light, strong, and fits very well. The best stock for accuracy has been my JAE, it's on my Loaded model rifle and I love it for a long range shooter.