Initially I had wanted to support a company that sells Linux-supported devices.
My first machine - a Gazelle (laptop) - had numerous issues on arrival. It'd randomly crash. Keypresses would get stuck and repeat. It was annoying. After sending it in, I still had random issues until I installed Debian, presumably it was a kernel issue - but for it to be shipped like that..was just bizarre.
My newest machine, I purchased a Leopard (desktop). It had been a few years, and I figured perhaps they'd gotten better at things. I was wrong. They shipped this machine, knowing full well how long it takes to boot - again, due to some kind of kernel issue - it took over 2 minutes to go from cold boot -> login screen, USB devices would randomly not work, just weird stuff.. I put in a ticket, but nothing ever came of it. I didn't want to send this machine back like I had sent my laptop (TWICE), so I ended up switching OSes again, using an updated kernel, and things seem fine.
I get that they don't really have control over the kernel that comes with the OS they ship. I'm not naive. It's just a bit silly that they'd be comfortable shipping a new machine with those kinds of issues to the point where the machine is either unusable or stuff randomly stops working.
As far as the "physical quality" of the machines go, I'm still happy with both of them. They are well-put-together machines, IMO.
However, I know that my next machine is NOT going to be from System76. It's significantly cheaper to just get a nice Dell or something.