This behavior is also true on Chrome/Firefox for Mac (s/ctrl/cmd/). Safari differs in that they correspond to bookmarks on the bookmark bar; I actually find this to be my preference.
Once I learned that it works for the bookmarks, I prefer it that way too. Especially for the bookmarklets for delicious, yc (thread-collapser), and instapaper: just mash the key, and I never need to touch the track pad.
On Safari+OSX, cmd-{ / cmd-} switch tabs. I'd still like a to-beginning / to-end key pair (maybe cmd-[], and reversed?), but that's pretty minor compared to not needing to navigate with a cursor.
