I use this feature, but it does find some false positives.
What I'd like though is to have two albums that have the same song in them store that song only once. And then let me play the albums in order.
As it is, I have some duplicates just so I can play the albums correctly. I even have one song which I copied the AAC version from a CD to my cassette album. It was a bit difficult, as there was data in the song that needed to be reset. (Copy it with a different name - add the track number - and then change the album from within iTunes).