It'd be neat if it pre-populated it with existing game scores (Will it?) Obviously it can't just yet but that'd make it easier to play with.

That's what I'm working towards. Unfortunately I haven't found anywhere that publishes XML/JSON feeds of match results for free.

The other thing I'm working on is a the allowing the user to pick winners in the knockout stages.

It would be nice to be able to fill in the results without having to press tab or clicking on the input box, by jumping to the next score box as soon as a digit is entered. In this way, one could fill all the results of a group in six keystrokes.