Having never seen previous versions of the movie, I cannot offer any comments about the extra footage. However, even after seeing only this version, the "complete" Metropolis, I can say that the movie is amazing and looks great considering how old it is. The recently added footage doesn't look quite as good as the rest of the film, but they did the best job they could with what they had.
The newly recorded version of the original score is also fantastic. The late-Romantic, Germanic style accompanies the film beautifully and creates a wonderful soundscape that fills your ears with wonder and drives the movie forward.
I was completely captivated when I watched the movie, even more than watching most modern films. The visuals are incredibly striking and prove that CGi is not always necessary to create great special effects. It is a privilege to watch a movie made with such care and precision. If you watch the special features, it describes the meticulous care that was taken in all aspects of the film; the kind of care that skyrocketed the budget, but led to a wonderfully constructed movie.
There is also a terrific documentary about the making of the film and its journey through the present. It describes the making of the movie, as well as the subsequent cuts that were made to the film. The history of the movie is just as fascinating as the movie itself.
I haven't said much about the plot of the movie because I'm sure many have recounted that in full in other reviews, so I chose to offer my reactions to the quality of the film and the special features contained on the disc.
An incredible movie.