See the full review for some disruptive (and possibly Chrome-copying) Safari user experience changes
Safari 4 also catches up to its rivals by offering suggestions of what you are looking for when you type in a Web address or search term. This worked well, but not any better than it does in other browsers.
Finally, the Windows version of Safari now looks and works much more like a standard Windows program than a Mac program. It has traditional Windows-style buttons and behaviors, which Safari lacked before.
Overall, Safari 4 is a mixed bag. The speed is great, but the design changes range from mildly interesting to downright annoying.