No, not really. There is still lots of room for improvement, especially if you want high resolution (retina or large display), 3D, multi-monitor configuration, and/or high levels of anti-aliasing. And providing stable 60FPS on 1080p can be difficult if you have mid-end or couple of generations old hardware.
Those gamers that demand 1080p@60Hz under load are a niche, not the standard for 'pc gamers'. And for those who demand it, shelling out a few extra dollars for hardware that exists (previously it didn't) is much easier than messing around with hardware voltages and crossing your fingers that your gpu is one of the lucky ones.
And frankly, the idea that gamers will flock en masse to linux for a few FPS is utterly absurd.
Oh, and Farmville ;)
Gamers use whatever platform their favorite games are available on.
I know many people are diehard about Linux, but it's a big commitment to switch and it isn't easy. Even so, many users might make the switch to find Linux seems to introduce a lot of headache and perceived restrictions on capabilities that Windows doesn't. Sure, they could probably tweak their way past the difficulties, but after troubleshooting on a wiki or in forums for a couple of hours it would lose the flavor for the masses.
Also, the least hassle I have had with migrating people to linux has been with people who really have no idea about computers, possibly as they have no expectations of how things should be and don't fiddle with things as much.
And besides, there is no real switching. I run osx, windows7 and linux mint, mostly, (often on the same computer, although I have found triple boot on hackintoshes to be a bit temperamental). Using a new OS doesn't mean you no longer use the old one. It doesn't restrict you really at all, it just gives you more perspective and a wider range of expertise. I highly recommend it. Linux mint is not a bad place to start as it is compatible with ubuntu (and therefore debian, to a large extent), but currently has a bit more polish. - http://www.linuxmint.com/download.php