Just gave the Safari4 beta a test run and I have to say: it feels like a step backwards to me. The actual rendering engine and js environment are stable and fast, so no problem there, but the typical user interface stuff that makes Apple great has been replaced with something that's not quite Mac and not quite Windows.
For example: The new title bar. The title bar acts as tab selector for S4 trying to emulate the "window-stack" system of Chrome. But it still uses the design from Windows (which doesn't work correctly under 7, but I'm willing to chalk this up as a beta problem, eventhough it hints at fundamental flaws in the implementation), aside from the new parts that were added to provide the tabs. So now we have a windows title bar, mixed with mac graphics and chrome functionality. What does that spell? FRANKENSTEIN, at least for me.
Other features that made Safari on Windows unique, like the beautiful font rendering and the wonderful widgets have been replaced with their Windows counterparts.
All in all, I have trouble seeing why I should replace any modern browser (Firefox, Opera, Chrome) with this.
What's your experience?