One I just realized: Gladiator was 6.1 DTS in theaters and is only 5.1 on DVD and BD. The Signature DVD retained the Dolby EX and DTS ES, but I don't have a copy and lack a 6.1 capable system to test.

I agree with HH that many times the mixes are the same, but what seems to happen frequently is that new EQ is added or compression is added somewhere in the work chain.

I'll have to do a full comparison of Batman audio in audacity. Forever sounds different in every mix, and more and more I find myself preferring the 4channel matrix.