I love the original musical, but I'm not a fan of the film. It comes down to the fact that I'm not actually much of a fan of the story. I don't really connect with any of the characters. Joanna is the one I come closest to relating to, but she's very much not the focus of things. But I love the music.
In the film adaptation, the music takes a backseat, so that Burton can do... well, pretty much the same thing he does in all his films. The man is nothing if not consistent. It's not that the actors are completely unable to sing. It's that they're not at the level needed to make the music shine. And since the music is why I'm there, I spend the whole film going "Well, this is disappointing."
If you love Burton, or Depp, or Bonham-Carter, it's all there for you to enjoy. Just don't think you're getting the full potential of the music. For that, you need to look elsewhere.