I personally think the friendly rivalry between the open-source Webkit engine (which powers Safari, among other things) and Mozilla (the Gecko engine, actually) is one of the best things to happen to browser development in years. The constant one-upsmanship can only lead to better browsers. Well, Internet Explorer will constantly be the limiting factor, but we can dream, can’t we?
Mozilla, particularly, is posed to reap some real reward. These JIT trace tree improvements will start showing up in 3.1 (I think), and much more so with the new Tamarin engine schedule for Firefox 4. The only viable Webkit browser in Windows, meanwhile, is Safari2, which looks and feels alien in Windows, as Apple has a strange insistence upon keep the OSX look, regardless of platform. I don’t know offhand the market slice that Safari for Windows occupies, but it must be infinitesimally small, even compared to Safari on Mac. Firefox, then, is the only truly compelling browser on the Windows platform to take advantage of this right now.