I miss this feature the most in all modern browsers and I know there are more people out there.
I guess if you have never used it back in Safari 4, you won't really miss it today.
But it has "saved my life" a few times, to be able to browse my history and see the complete page visually represented.
Sometimes one doesn't remember the exact URL or the address of the website visited at all.
Other times you visit so many pages at once, trying to find something, that later it's insanely difficult to make out which website it was.
Thumbnails in the browser history can resolve that issue.
(Weak point) It makes for eye candy and like the devs cared.
That's my only wish for this browser. Everything else is more or less fantastic.
I would also more so make it look like the Tab previews (Squares) instead of Cover flow, which might be unnecessarily difficult to reproduce and also is patented.
