Eagerly awaited musical 'If/Then' is a winning blob, with many kinks to be worked out

Ever buy an appliance with so many working parts that you feel the need to read the owner's manual again and again? A first sitting through "If/Then," the charming and ungainly new musical trying out for Broadway at the National Theatre, engenders a sensation like that: It's a shiny new thing you're eager to play with, but doesn't prove to be entirely user-friendly.