As most people know now, Apple's released a beta for Safari 3 for both Windows and Mac. It took me awhile to figure out why, since I've always preferred the extensibility of Firefox over Safari. I found it interesting to tout it as being faster on JavaScript rendering than IE 7 or Firefox. That wasn't enough of a reason for me to switch.
This morning, I realized it was to gain developers for the iPhone. Now that developers can harness Safari on iPhone for widgets and other applications, it makes sense having a score of new developers that might not own a Mac but do develop for the iPhone. These could be free (like so many OS X apps and widgets) or commercial (also like so many OS X apps).
I'm guessing, if it works on Safari 3 (either platform), it'll run on iPhone's Safari.
UPDATE: Crave agrees with me.