Before watching the movie:
Well, I liked Hairspray, and Johnny Depp disappears into his roles entertainingly. A John Waters musical with Johnny Depp should be fun. Off the top of my head I can’t think of a movie where Depp seriously sang other thanThe Nightmare Before Christmas, so I can’t predict how well he’ll be able to lead a live-action musical.
As this is a musical set in the 1950s about kids in leather jackets and their relationships, I’m expecting a movie more like Grease than Grease was.
EDIT: I have been reminded that Johnny Depp was not in The Nightmare Before Christmas. Trying to hear him in Jack Skellington is probably part of the reason I have a hard time identifying him.