My wife and I and the kids rented this out a couple of nights ago. All of us had already seen the musical on stage and enjoyed it and enjoyed the movie for the most part.
I was kind of disappointed that a couple of the songs were cut ("The Name of the Game"-available on a deleted scene however and "Under Attack") but I wouldn't necessarily say that it detracted from it too much. I think that they snuck in a new song at the end (the wedding dinner song sung by Pierce Brosnan)
I thought that they were (obviously) able to do props and sets much better given the movie format and the entire cast looked like they were genuinely enjoying doing the movie. Some of the parts in the movie were a bit risque, which was a bit embarrassing since we were letting our kids watch it but I don't think they picked up on anything.
The singing wasn't as good as the stage version I saw nor the original cast recording but that's o.k. I think it was nice that they let the cast do all of their own singing.
One minor nitpick on the casting. While meaning no disrespect to Meryl Streep (who is still rather attractive despite her age), I think that they probably should've cast some younger actors and actresses given that Sophie's mother (Donna) should've been chronologically 39-40 years old since, according to the story, she had Sophie when she was about 20 and that Sophie's age is supposedly about that at the time of the story so it probably would've made more sense to cast some younger and not quite-so-middle-age actors and actresses perhaps for the parts of Donna, Bill, Sam, Harry, et. al. but in the end it doesn't matter a whole lot.
When it comes right down to it, the movie was FUN which I think is the most important thing and what ultimately makes it work. I'm on the fence about whether or not I'll buy it but probably will when it gets discounted.