I'd really like to see this one get implemented. For the past few years I've been using launchd to run an AppleScript every 2 minutes, which checks to see if iTunes is now playing a different song than the last time it checked, and if so, write a file. I wanted to use the Track Change Items, but find it extremely annoying to have an app launch and quit (thereby changing the foreground app) every time the song changes (or I change the song). And you shouldn't have to try to load the text or anything like that - just use OSADoScriptFile, or use the individual steps if needed, and don't forget to save the script back to the file (if it was a compiled script) so changed properties get saved.
I agree that the potential benefits of this feature outweigh the costs/risks. My major concern was with the security of running arbitrary items in a folder, but I think it can be done in a reasonably safe fashion if care is taken.
By the way, that link to the forum post is broken because it points to the old forums. I think that it's a reference to either this or this thread. Funnily enough, the first of those threads was started by you!