I watched Mark Kermode's video review of this on
http://www.youtube.com/watch?v=61UolzFTVPI
before seeing the film. I agree with every word of it. It's a great review for a really odd movie. Do watch the review.
I think Mamma Mia is a strange movie because it was made for we ageing farts who still hanker for a LIFE and that's why it did so well at the box office; grey power rules! Cooooool.