I got the system back, and it seemed to work, but now I was getting a lot of crashes. I tolerated it for a couple of months as it wasn't so severe to make the system completely unusable, but I eventually got sick of dealing with it. memtest immediately reported some severely damaged RAM, so I emailed System76 and again, after a protracted paperwork/support process, they mailed me replacement parts to install myself (the only alternative to shipping the whole laptop back off to California; the disk is encrypted, but still was not looking forward to the potential of a careless tech wiping it and another $80+ bill to make sure it got back to me within the month).
I installed the new RAM modules (and I'll say that it was quite easy to take apart, only exception being the keyboard ribbon, much better than my old MBP) and things were going better, but I still get full system hangs in 3D games. I am concerned that there is a hardware issue with the GPU. Haven't cared enough to tackle that one seriously yet, as I do most 3D stuff on my desktop, but it's really annoying.
If System76 was better with their support processes, these would not be such a big deal, but with their non-cooperation in getting shipped repairs performed and returned quickly, inability to contract out or reimburse for local repairs, long RMA processes and limited customer service availability (no weekends, hours something like 9a-4:30p Mountain), it's just not worth the hassle.
Next time I will get a powerful Dell most likely. I just wipe them immediately and put Arch on anyway, so no concerns about bloatware/spyware/whatever.