I used to run Linux exclusively, but a couple games I play were pretty bad in the WINE environment about 6 months ago so I have a dual Windows 7 + Linux Mint install right now. The problem with Linux is that using WINE to run games in 64 bit is pretty annoying to get going, but gaming really should (and gradually is) leaving 32 bit behind.
The most attractive thing about Linux is that it's even cheaper than windows and miles easier to use now than say 10-15 years ago, with lots of good software that is competitive with high-priced windows/mac stuff while open source. Stuff like SimpleScreenRecorder (great recording software) or GIMP (photoshop) is pretty handy to just install. I'd like to see it become competitive with Windows for gaming (Mac never will with its pricing, and screw Windows) but right now compatibility is still a hassle.
For most people right now building their own machine based on their price point (with 8 GB RAM, dedicated graphics card, at least decent processor) and slapping on a 64 bit Windows install (can't imagine why anyone would use 32 bit at this stage) will work best for gaming and save a lot of money.
League can be played in Linux though. There's an audio glitch and you have to install some extra stuff through WINE to get the store to work, but I played it in Linux for quite some time.