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As for Safari on Windows, I think there's a multitude of issues that are holding it back:
1. There are a majority of people out there who just don't care what they surf the web with. They use IE because it comes with their windows machine and that's all they care to use. They don't want to be bothered with installing an alternate browser. This is the #1 reason why IE still commands 75% market share: not because it's a good browser, but because most people are lazy or too afraid to install something else.
2. For those who DO care, I think most are uncomfortable that Safari 3 is still considered a beta for Windows. The concept of using beta software could fly when Firefox was the only real alternative to IE, but with Firefox already well established as a stable product, people would rather flock to it than something still seen as experimental.