Ask the Jedicouncil at the Official Site answers this plaguing question from fans since the two versions were released. Here's part of the answer:

At the last minute, George felt the wedding scene needed the affection of Padm? taking Anakin's mechanical hand, so just a few days before Celebration II in Indianapolis we shot it and inserted it in time for the D-cinema version.

That addition is by far the most noticeable change, but we actually made over 70 enhancements for D-cinema. Most involved sharpening, tweaking wipes and color adjustments. However, there are a handful that are definite visual effects changes. I'd be curious to hear if any fans have found any of the other changes.