QUOTE(NRGetic @ Apr 3 2008, 18:08)

saving ratings into the mp3 files
No plugins needed. If you want to create a new tag, just open the File Properties window and choose "Add New Field" in context menu. For more comfort you also can add the field name in Preferences > Advanced so that it is shown with a more friendly name. To quickly set tags to a small set of values (esp. for ratings, foo_quicktag offers the possibility to assign keyboard shortcuts).
QUOTE
the art
I don't know, I stick to the folder.jpg "standard".
QUOTE
Playcount would also be a nice thing to write directly to the file.
Use
foo_playback_custom instead of foo_playcount.