Access tabs directly in Safari with ⌘+1..9 keyboard shortcuts?
This is now the default behavior of Safari 9.
Edit: This answer pre-dates Safari 9.0 where Apple correct the Cmd-# behaviour.
You can, but it takes an extension to be able to do it.
You'll need to install Safari Tab Switching by Olivier Poitrey to be able to use ⌘+1..9 to access tabs directly. It's a great extension if, like me, you've got these shortcuts in muscle memory from working with Google Chrome for so many years now. It's also open source and available on GitHub for the curious.