As of version 4, iTunes has a "Replace Existing" option when users are re-importing CD tracks to replace existing tracks. The problem is that iTunes will only allow this option if the ID3 info for the CD tracks and the current iTunes tracks is identical. This script writes the writable info from selected tracks to the info of a CD; when you re-rip, the CD track data is already the way you want it.
(Note: In order to launch this PowerPC-era script on an Intel machine, it must first be opened and then saved using AppleScript Editor, which is located in your /Applications/Utilities/ folder. More information is here.)
App displays files in iTunes Media folder which are not in iTunes library
Remove iTunes tracks disassociated from files
Create a text file containing an alphabetical list of chosen tag data
Change file type to make selected AACs bookmarkable
Save the display artwork of the selected track to a file
Show files of selected iPod tracks in the Finder