Playing around with the new Safari 4 beta and am impressed with the Top Sites feature.
Top Sites tracks your 12 most visited sites and surfaces them as a single page. For extra brownie points it also loads each of those sites so if you click through to the full size of the screenshot below you'll see that the default "yahoo.com" panel actually loads the Yahoo!7 (Australia) front page. And as I was logged into Flickr, the "flickr.com" panel shows my actual Flickr frontpage. If one was crazy enough to browse with a full-size 1920x1200 Safari the headlines on various News front pages actually become legible. :)
Full search of your browsing history, including text within browsed pages is pretty nifty too.
Unfortunately for Apple, I'm not going to be switching full-time to Safari any time soon. My Firefox setup is too comfortable, and Safari is no more secure than Firefox or IE.