Why Safari for Windows?
A common question that seems to be heard now that Apple has released Safari for Windows is "Why?" And while I don't know the real reasons, I have my opinion on the matter.
For Web Site Developers
When asked why Safari is being released for Windows, a few people have said that it is intended for developers to be able to check their sites without having to own a Mac. It'll definitely be nice to have something on the PC that comes close to comparing the two. The unfortunate part is that Safari 2 is still the major browser right now and it's more troublesome than the latest WebKit. Every problem I've run into with Safari in the past 6 months has already had the issue resolved in WebKit.
So, while the testing environment will be nice, it won't really help us developers in the short term.
For iPhone Developers
One of the announcements to come out of the keynote was that Safari was going to be the development platform for the iPhone. Well, if you want people to develop for the iPhone, you better make the platform available to the most number of people. No sense keeping iPhone developers locked into use a Mac.
Adobe and Apple sitting in a tree
Adobe AIR (Apollo) uses WebKit as one of its core technologies which works on OSX and Windows and eventually Linux (or so I've heard). Imagine AIR integration with the iPhone. Okay, that's not necessarily why I think they'd want to use the same platform but I think both companies benefit from using the same platform. You could theoretically make an application that could work as a desktop application, as a web application, and as an iPhone application. Win-win-win.
A couple years from now, Apple could even use the by-then-tested phone-based Safari and license it out to other phone manufacturers or use it as leverage as they expand onto new carriers. They could easily start playing in Opera's mobile arena.
While Adobe and Apple may not be working together specifically, they both benefit from using the same cross-platform technology.
The New Dawn of Browser Wars?
For the average user, especially the average Windows user, much of this they certainly won't notice. Certainly not within the next 6 months. Depending on the developer uptake, though, things could begin to shift in the new year.
Firefox has definitely put a dent into the behemoth that is Internet Explorer and with the introduction of Safari for Windows, things could get interesting.