Spatial navigation is indeed great way to navigate with the keyboard. I wonder if anyone seriously uses Tab-based keyboard navigation?
There's more smart keyboard navigation in Opera:
• Cmd+Enter to log in on page which has autosaved login.
• Cmd+Backspace to delete last path component of the URL.
• Space at bottom of page clicks link with "Next" in the label.
• '/', text, Enter navigates link with given label (as opposed to '.' + text which searches page as you type).
• And (a rather quirky) '1' and '2' keys switching previous/next tab. It's much easier to reach with left hand than combos such as Cmd+} or Alt+Cmd+→ used in other applications.
The last two have to be enabled in prefs.