Dupe of http://news.ycombinator.com/item?id=1438255, but I think it is worth another look in light of a few things:

1. Advances in web application technology like HTML5, Sproutcore, and so forth.

2. New "platforms" like smart phones, tablets, and ebook readers where Microsoft doesn't dominate.

3. Getting back to point #1, the possibility that nobody uses desktop applications, where by "nobody," I mean "fewer than 10,000,000 people," to borrow Joel's phrase.