According to TheForce.net, in the May issue of Empire Magazine Rick McCallum spoke about the digital version of Revenge of the Sith. Interestingly, he discussed one of the major differences between the film and the digital format.
"The digital version of the movie will be different from the version that goes out on film. That has to be locked down so much earlier, whereas the digital can go right up to a week-and-a-half before the film comes out"
The article went on to talk about how the digital version of Attack of the Clones was also different to the version that came out on film, most notably, the shot of Padme holding Anakin's mechanical hand at the end wedding scene.
Supposedly, the digital version of Revenge of the Sith will be longer than the film version. There is some speculation that this is a “reward” to those theaters that have upgraded to digital projecters.