I saw the movie today, and I must say I thought it was extremely enjoyable! Somebody else said the songs seemed shoehorned into the film and while this is true, I don't think it should be taken as or expected to be anything other than what it is, a feelgood summer movie with great songs in it that you will leave with a smile on your face (even if it's against your better judgement!)
For me, Christine Baranski and Julie Walters were the best thing in it, and along with Meryl Streep they worked wonderfully as a trio. I don't think I've been to see a film in quite a while in which it was so obvious the actors thoroughly enjoyed making it.
Pierce Brosnan wasn't the best singer, but he was better than I'd been led to expect, and I found myself actually quite liking the quality he has to his voice.
It wasn't Shakespeare, but it was a very enjoyable afternoon, and I would find it quite hard to fault. If I had one niggle it would be that the fathers' characters (in particular Colin Firth and Stellan Skarsg