I finally found the fix for a major annoyance I had when using my mac: that I had to use the mouse for every dialog box that popped up. A simple yes/no/cancel dialog from Firefox or Safari is impossible to navigate with the keyboard with Apple’s default settings! The solution turns out to be very simple: in the system preferences, go to the Keyboard and Mouse pane, and select the Keyboard Shortcuts.
If you change the last option to “All controls” you can now use the Tab-key to choose Yes/No/Cancel and other buttons in any screen!
If only Apple would allow you to delete files in the finder with the delete-key (seriously, why call it a delete key if you can’t delete stuff with it!) I’d be happy with OS X.