In response to an early question: yes, there is "special" material on the disc.
To quote Amazon:
-Director's cut of the film (anamorphic widescreen)
-Original concert film (full screen)
-Interview with director Adrien Maben
-Pompeii map and history
-Lyrics
-Photo gallery
-Album graphics
-Odds 'n' Sods
The "Director's Cut" has new stuff added, in the form of new effects and suchlike inserted directly into the original concert edit. What this new stuff consists of exactly, I'm unsure, as I have yet to receive my own copy, but, to further quote Amazon:
"Maben's cut goes to great lengths to lend the film a more contemporary feel... The anamorphic, 16:9 director's cut interweaves the Pompeii performances with fascinating but distracting interviews and music snippets filmed later (mostly during the recording of Dark Side of the Moon)."
...and...
"there are some space/planet features that are kinda confusing, as well as the CGI art of how Pompeii would have looked"
...and so on...
I'm ecstacic this was finally released. While I think Waters is a genius, he's more lyrically and socio-politically so. Barrett was a longtime favorite, but I've drifted away from the whimsical over the years. In the end, the Mason/Wright freak-out period, as best exemplified by Pompeii, has stood out as their best material in my mind.