Here are some issues:
The timestamp takes a few seconds, before it starts.
Jumping is not possible. The bar and time moves, but the track keeps
playing.
When opening another window, or switching off the screen (manually or
automatically by powersave), the timestamp freezes. After skipping the
track, it works normal again.
the play / pause issue, as me pycage and me described.
Maybe the bugs appear, because I am using the svn build?

I have an idea for cover art: Mediabox could provide a thumbnail of the
cover art in the /tmp folder, that the widget could load and display.

Why not integrating the FM radio and the widget in mediabox?

What do you think?