Most enjoyable - thank-you for this! I made some comments on UKPA's forum before noticing this discussion.

To repeat:
- It's a pity we can't see a full leaderboard for each day's puzzles...
- ... also that there are no times shown.
- A final nice touch to the interface would be right-click and drag for multiple empty cells.
- Make competitive entry valid only on that specific day (or just last 7 days), then we can discuss puzzles after they have elapsed.

My suggestions for puzzle availability and leaderboards are based on those at http://www.kwontomloop.com/ which I think works very well.