Update [20 June 2008]:
My initial reaction is positive. I use Safari most of the time, but Firefox has fixed some things that make it work more like Safari on Mac OS (purely cosmetic).
1. When I drag an image from a web page to my disk drive it now drags a translucent version of the image. Version 2.0 just displayed a rectangular outline.
2. When I use the “Zoom” widget it causes the window to maximize. Version 2.0 just resizes the window. I think this should not be called Zoom, because (see 3.)
3. New to version 3.0: Full Zoom. Web pages “scale in the way you’d expect them to, with all the elements of a page’s layout expanding equally…”[source]
One thing they didn’t change: The tab key moves the focus from link to link within a web page. I prefer the tab key to move the focus from text box to text box. There may be a way to change this in the settings, but I haven’t found it. Can you change this setting on the Windows version?