Why Safari will double its market share
Although most people don’t change default browser, people who use Safari at home will be tempted to use it at work on the Windows box they’re saddled with… Particularly because of the more familiar font rendering. As a result the number of Safari users will appear to double (different IP addresses, cookies, etc). This sudden increase will be hailed as remarkable, causing other people to try out the new kid on the block. As pointed out by John Gruber, Google will pay for the port by sharing ad-revenue from Safari’s search box. Apple can also expect to leverage the Itunes halo effect, especially if it bundles Safari with Itunes.
Now a wild guess: Just as Itunes is the interface for the Ipod, Safari will be part of the required interface for the iPhone, letting you share bookmarks with your phone among other things (Bonjour is installed by Safari for windows).