The other DrC and I saw the film Mamma Mia this afternoon. Several years ago we saw the stage version in Las Vegas. Both were entirely worth watching, although quite different experiences.
The stage version uses a quite limited set and props, requiring imagination on the part of the audience. We found this requirement not to be a detriment, but an advantage. The artificiality of the musical theater experience is less confrontational in a live theater setting. Folks in costume down on the stage bursting into song seem less "wrong" than when that same action happens on screen.
The film, on the other hand, was set on something that sure looked like a Greek island - very craggy and beautiful. The inn the mother runs is the real, dilapidated article, not just a piece of modern sculpture you are asked to imagine is an inn. The film's cast is larger than the stage version, with many picturesque locals adding verisimilitude.
Oddly, the realism of the film is pretty but it makes the "bursting into song in inappropriate settings" which typifies the musical genre more difficult to wrap your mind around. I wonder if this isn't what killed the movie musical, while its stage relative survives?