OK, I had a look, and the comments from empeg seem to suggest that
they do intend to release some sort of API. Does anybody
have an idea of when that might be?

I really want to be able to customise the UI because I don't believe
that ANYBODY is good at UI design; it requires that the person who
writes the software knows how I relate to my music.

The only good UI is one which lets me change how it works.

On a barely related UI note, yesterday by accident I discovered
the ability to search for playlists/tunes by year/title/artist/genre.
Should I have been aware of this through any documentation?
This is a cool part of the UI, and one which would lend itself
nicely to customisations.

Richard