I'm upgrading some sites today and never knew about this nasty little glitch that left files behind. We have over 2gbs of lost and disconnected images and it's going to take ages to sort through all these folders, one by one and delete them from the mix.
Sure would be a good feature to have,
or even a way to know that the file needed to be fixed, without bumping into it via a thread like this.
Other than that, it was the smoothest upgrade I've done yet.