I figured out some of my Just Cause 2 and Red Faction Guerrilla woes: 2nd monitor. Turn it off and Guerrilla seems to work. I didn't have a 2nd monitor last time I played Guerrilla.
Whaaa? I have both of those, and two monitors, and they both work just fine for me (NVidia GTX 460, Windows 8 Pro). What problems were you having?
I get screen tearing after some time. It might be a heat issue now.
What about the fact Steam just flat out refuses to sell games with GFWL to a lot of territories.
It's probably because of all the Antitrust issues Microsoft has on a regular basis.
Tearing tends to be visible when you're not using vsync. If the game doesn't handle the framerate properly and your card is really powerful, some games could also run the card too hot if you have vsync off. I would think most games wouldn't do that, but since I use vsync all the time because tearing drives me nuts, I'm not sure how many have over-heating issues. (Also because my card has never overheated or come anywhere near doing so, and the fan never has to work at anything close to full power, because it's so well-designed)
I'd suggest forcing vsync on. If there isn't an option in the game, then set it in your video card's own control panel. E.G. Right click the desktop, hit NVidia control panel. Click Manage 3D settings, and either change it in the global settings, or make or find a profile for the game(s), and set VSync to on. I also have triple buffering on (which tends to help the framerate, particularly when you're using vsync). You can also try adaptive, or if your framerate is low, adaptive (half refresh rate), but adaptive turns off vsync if it can't get a good enough framerate, and I would suggest trying vsync and triple buffering before trying adaptive and triple buffering (because you may not need adaptive, especially for older games).