Thanks for the advice! Yeah, I'm already fairly careful about updating drivers, but I'll certainly take that into account. I have used Linux before, but that was Slackware quite a few versions ago, so I expect that Ubuntu/Mint/any other distro I might consider for gaming will have some differences. I wasn't a particularly advanced user at that time, although I knew at least the basics.
I never use a controller -- grew up using only keyboard and mouse, and controllers feel clumsy and awkard to me -- so that won't be a problem.
PlayOnLinux sounds quite useful. I'll certainly keep that in mind. Any advice about wrangling Steam is always appreciated, since that's something I've a few concerns about, having had large troubles with Steam in the past (albeit on Windows and when Steam was relatively new). I figure there's no way reinstalling Linux can be as much of a pain as reinstalling Windows 95 from floppies, so I'm cool with that.

Good to know, though.
I've heard that Nvidia cards have tended to work better with Linux than AMD cards in the past, but I'm having trouble figuring out whether or not that's still true. Do you know? I've been using AMD processors and video cards for the last few years, and would rather continue that if it's reasonable to do so (partly 'cause they're less expensive, I admit, and partly because my last two computers have been the most stable I've yet managed), but I'm not against switching back to Intel and Nvidia if that's the way to go.