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.
Restore each selected track's artwork from an image file stored in its Album folder
Convert selected tracks and replace them with converted versions
Change video kind and video related tags of selected video tracks
Edit a selection of iTunes tracks' tags in single window
Export selected playlists as individual XML or M3U files
Create text file listing tracks common to and exclusive to two playlists