The tab bar on the top (that, by the way, had inconsistent window color with the rest of OS X Leopard’s UI and doesn’t look good in Tiger, either) is replaced by one on the bottom.
Note the inclusion of the plus button on the right hand side of the bar to add a new tab.
Also note how similar it looks when compared to Firefox’s.
The RSS icon is updated to a bluish-grey color and matte look not dissimilar to OS X’s Graphite theme.
The loading indicator has taken a new look (it actually says “loading”). When the page first loads, it takes a dark blue appearance. This color fades to white when the page almost completes.
The default toolbar now changes to a minimalist set of tools: navigational (back and forward), spatial (address bar, add bookmark) and inquirial (search.)
The Customize Toolbar menu itself (accessible through the View option) carries several new tools: show/hide Bookmarks bar, show/hide Downloads, and, most notably, one-click Web Inspector access.
Did I Overlook Anything?
I probably did, because there are many other subtle changes in Safari 4 (smooth transitions on the loading indicator is one easily overlooked) so let me know if you found them!
Update: Here’s Something Else New
Safari 4 now features a transparent progress bar that overlays while you’re waiting to view a PDF file.