I'll have more to say about it later, but I saw Mamma Mia, it was partly-to-mostly awful, and I can't wait to talk all about why. A few key points:
1) Watching people act as though they are having fun is not the same thing as having fun. (I have a similar opinion, this one more controversial, about The Blair Witch, as regards things that are frightening.) Watching people screech like 9-year-olds and stomp around like giant city-wrecking monsters on Ecstasy is not the same as being a witness to ecstasy.
2) Salon.com's Stephanie Zacharek is spot on: James Bond can't exactly sing, but as an actor he GOES FOR IT, and god bless 'im for it.
3) Speaking of effective expressions from the UK, to review this movie in five words or less I found I had to go beyond American English and use British English, which in general is far better for the occasional verbal sniper-shot. It's not that the film was poorly made (which it was), or that it was not fun (which it wasn't, really, and certainly not as much as it thought it was). It's that, all in all, this movie is just utterly pants.
Pants(!) Noun/Adj. Nonsense, rubbish, bad. From the standard British English of pants, meaning underwear; also a variation on 'knickers'. E.g."The first half was pants but I stayed until the end and it was actually a great film." [1990s]
Exclam. An exclamation of annoyance or frustration. From the noun, (above).