My life has changed thanks to Joe. Suddenly my tab key is more useful on my Macbook. I can now tab through my dialog option buttons. There's an obscure setting in the System Preferences > Keyboard and Mouse > Keyboard Shortcuts > Full Keyboard Access (set to All Controls). Or you can press ctrl-F7.
This makes so many things much easier to do with out having to constantly use the mouse to move to a button and click.