Safari available on Windows. Why ? One word: iPhone
A lot of web 2.0 applications have problems with Safari. This is well known and has moved a lot of OS X users over to Firefox. Personally I have to run both for my day to day websites. Since Safari is the browser of choice on the iPhone Apple needs to move the marked. By making Safari a Windows application Apple just added millions of potential developers and testers to its new iPhone platform. User generated content is the new hotness and Apple Safari must follow the marked leaders in order to stay relevant.
There are some bugs though. Clicking on the bookmark button instantly crashes Safari.