At today's WWDC Keynote Steve Jobs announced that similar to iTunes, Safari 3 will now be cross-platform. As an interactive developer this announcement was not welcomed by me because instead of two major browsers, I'll have to develop (non-Flash) sites for three (IE, Firefox and Safari).
I suppose the case could be made that interactive designers and developers have had to create for three browsers ever since Safari for OS X was released, but the market share of Safari (and those users who use Safari over Firefox on their Macs) was quite small. By introducing this to the Windows market, the task of testing on every browser becomes a growing problem, not a shrinking one.
So be sure to download and install the public beta of Safari 3 from Apple's website (http://www.apple.com/safari/), as you'll need to add Safari for Windows to your CSS and JavaScript testing suite.
Some times Flash's ability to run identically across all browsers on any platform just makes it shine even more. Today's Safari announcement makes the decision to develop for the Flash Platform that much easier.
Update: Todd Dominey and Shaun Inmann both weigh in on the issue with some good points:
Todd: "Speaking of web development, the release of Safari for Windows is fantastic news. Finally, Windows developers will be able to preview/test their work in Safari, without owning a Mac, and have a pretty accurate (if not identical) representation of what Mac users will see."
Shaun: "It took me quite a while to get onboard with Safari when it was originally released for OS X: the prospect of having yet another browser to debug didn’t endear Apple to many developers. But Safari on Windows is another story entirely.
Assuming the rendering engine is consistent (I wonder how it will handle anti-aliasing) this is a huge windfall for Safari users on the Mac because even moderate adoption on the PC means more attention payed to the rendering engine’s quirks which will result in a better experience for all."