So, what's wrong with iTunes? (or what more would you want?)
Radix: Single biggest flaw, as far as I'm concerned, is the inability to script the folder hierarchy.  If I want All albums folders to be prepended by the release year I should be able to do that.Edit:  Also, sometimes I have correctly named mp3's, but I haven't tagged them.  Itunes gracefully renames my files to 'unknown' removing any trace to the correct name.  And, if the files were in a folder prepended with the album year iTunes will kindly create a new folder to hold the files to leave the album art in the original folder.  (okay, that last one is Windows only)