Quote Originally Posted by Dr Unne
I can play NWN and Ragnarok Online in Linux, and every other game I care about (Baldur's Gate, old games like that). I don't find myself needing Windows for anything, but it depends on what you use your computer for, and what your priorities are.
But you need to use an emulator :p. And from what I've heard, it can be a bit tricky to get games working under WINE and such. Also, you do get a performance drop, as it takes some cpu power to do the emulating.

And yeah, like Samuraid said, you can have both operating systems installed, and get a choice between them when you boot your machine.