I always thought people don't use non-Windows cause of software. For example I have a friend that wants to use Ubuntu but also wants to use itunes. I'm sure a lot more people want to play games, use microsoft office, etc, too. Frankly if microsoft were to go away and die, then we'd have more software geared towards linux/os x.
The way I see microsoft, they're very manipulative. For example, instead of making the most powerful video game console, they pay off developers for exclusive titles or game features. I think in the OS department they exhibit the same strategy where they aren't doing the simple make the best product so it will sell the most strategy. While it may be an effective strategy for a business to be sly and manipulative, the consumer gets screwed. For the same reason I hate cell phone companies. Why can't they just have us pay the actual value for the phone and charge a fairer monthly fee?
So it would be great if microsoft would die. We'd have less manipulative proprietary crap and more innovation.