Looks good. At first I was concerned that modifying the time format would affect how it appears in Mail, the Finder and such.
After testing with Mac OS X 10.4 and 10.5, I find the "Medium" format you mention only seems to affect the Menu Bar Clock. The "Short" format affects Mail and Finder views.
The other thing to note is the Date and Time Menu Bar Clock settings. It is easy to have the Day of the Week duplicated for example, and that is where you want to display the seconds if desired.
Let's get some more input on this.
Any chance you figured out how to do this for Snow Leopard?
I did this before, and when i migrated i could see that the change i made in Tiger, carried over, (that is there was a date in my medium clock setting) but it doesn't show in the clock in my menu bar...
Is there a fix?
Maybe Lion will bring this back... or better still offer the ability to put what we want with less complication?