This script uses the UNIX qlmanage command to display a Quick Look window of the selected track(s), which can be audio, video, and, perhaps most usefully, PDF, whereby Preview.app is not necessary. Also handy for playing a single track out of playlist context. Need I add that a keyboard shortcut makes this very handy.
Caveats: 1) under Leopard a media file will begin playing immediately, so the script uses a hack to prevent this, 2) under Snow Leopard and better the QL window's title contains "[DEBUG]" which cannot be suppressed, and 3) the QL window can only be dismissed by clicking on its close box.
Renumber order of selected tracks
Convert selected tracks and export the converted files to a new folder
Perform search-and-replace on text in your choice of tags
Set year of selected tracks to their release date's year (if available)
Copy Comments tag to Description and/or Long Description tag of selected track(s)
Rename selected tracks' Song Names with their filenames (minus extension)