My folks found it funnier than I did.

Rating: 5/10 (20 July 2008)

Me? I found it slightly funnier than GET SMART: THE MOVIE. But, only to the extent that I was able to sit all the way through to the "Waterloo" number during the ending credits.
Aside from that? It was just a musical remake of BUONO SERA, MRS. CAMPBELL. At least, as far as I'm concerned.
For those who might not remember it? BUONO SERA, MRS. CAMPBELL is an old Gina Lollabrigida movie where she has told each of three GI's she met, during WWII (Telly Savalas, Peter Lawford, Phil Silvers), that her daughter is also theirs. In MAMMA MIA!, each of Sophie's possible fathers were counter-cultural teens during the 1980's. And, _none_ of them were told by Donna--Meryl Streep--that one of them had fathered Sophie.
That and the Abba songs are the only major differences between the two films. But, again, only as far as I'm concerned. As stated way above, both my parents thought it was hysterical.
The only belly laugh I had, however, was seeing Pierce Brosnan in that blue jump suit during "Waterloo." Oi vay (and I'm not even Jewish)!