I want to ditch windows too, but for a number of reasons:
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I like to play the occasional game with my housemates over the lan, or on the internet
Day of Defeat and Dawn of War is all, really...
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I don't have the time these days to spend all day tinkering with computers - I'm trying to spend more time on my creative hobbies - writing and photography. Windows is just easy, and easy to get help/advice for if you need it.
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Find me a way of playing the odd modern game (I know some DO run on Mac) and I'm sold!