Most of the bad reviews for this film come from the fact that people just don't realise that it's not supposed to be a magical film for adults and children alike. If anything, adults should be able to see the humour in this more than the children!
Right from the opening scene, everything is so ridiculously overdone, that you either feel ridiculous for sitting there and watching that, or, like me, you are in stitches. It's idealistic to the point of vomiting, but in fact as the film progresses it becomes clear that everyone else is just as nonplussed by Giselle as you are.
Buy it and watch it, but if you want to enjoy it then it's important to not take it seriously. Especially if you listen carefully to the words of the "Happy Little Working Song" (Never has a princessy tidy-up song been so literal!)