The biggest problem was the mistake of not sticking to the stage script, thus eliminating the jail scene (and the amusing number "In the Big Doll House"), and changing the circumstances under which "Without Love" is sung (making it much more difficult to sympathize with Link). Likewise "Mamma I'm a big Girl now" is greatly missed, and the two new songs "The Lady's Choice" and "New Girl in Town" are not especially happy additions to the story.
It was never likely that the younger generation from the original cast would get to repeat their roles on film, as all of them were in their mid to late twenties when they opened the show. So it was inevitable that actual teenagers would have to take these roles on screen. Newcomer Nikki Blonsky does quite well as Tracy. If she lacks the glow that Marissa Jaret Winokour had on stage, she's a cute and appealing presence with a sweet singing voice. Brittany Snow is appropriately icy and pretty as Amber. But Amanda Bynes disappoints as Penny (with unimpressive singing) and Zac Efron fights a loosing battle with the re conception of his character.
Its a bit more strange that none of the adult leads from he original Broadway cast were permitted to reprise their performances. If no one is superior to their stage predecessors, none of them disappoint. John Travolta's make up is less than flattering, but his Edna is a warm and likable character. Christopher Walken is also likable and charming as Wilbur. Queen Latifah isn't as brassy as Mary Bond Davis, but she is an apt choice for Mabel and has never been in better voice. Michelle Pfeiffer successfully plays up the sex in Velma to good effect, and the singing just strong enough for the role. Perhaps the happiest newcomer however is James Marsden, with a pleasant singing voice and broad toothy grin that's just perfect for Corny Collins.
Hairspray was pleasant summer fun, and is more than easy to sit through, but it is frustrating to see that it could very easily have been a flawless stage to screen transfer, which it wasn't