I know when I'm fixing up ID3 tags on lots of albums, I get goin pretty fast and tend to forget when I have lots of items selected. I think maybe a confirmation when you are changing the ID3 on more than x amount of files would be helpful. I haven't changed my entire library yet, but I have messed up some albums/crates. I think also that Album/Comment is a field that gets changed often by mass. Although Artist/Song could be less popular, song especially. Maybe always have a confirmation on mass editing of song title?

Just a thought.