Mr. Banks is obsessed with his work and his place in society. As the show evolves, it becomes more and more clear that his ability to have fun was beaten out of him by his nanny, Miss Andrew. Mrs. Banks is a former actress who worries about her ability to be what she's expected to. The children, Jane and Michael, have chased off 6 nannies in 4 months. Then, Mary Poppins comes along. Her "games" are aimed at healing the family.
So the whole thing is much darker and more psychologically focused than the movie was. This will, of course, go over the heads of chidren - and there were plenty of youngsters in the audience. They can enjoy songs like "Jolly Holiday." with the statues in the park coming to life. The choreography is definitely one of the strong points of the show, particularly in the numbers used outright or adapted from the movie. Fortunately, Gavin Lee as Bert was well up to the challenges of dancing his part. He needed some elaborate bodily sign language for "Supercalifragilisticexpialidocious" but the real display of his talents came during "Step in Time." I'm not much of a fan of spectacle, but I can't imagine anyone would be unimpressed by his tap dancing on the ceiling. (You can see the harness wires, but you aren't likely to care.)
I liked the music better when I was 9 than I do now. Of the new songs, the confrontation between Mary Poppins and Miss Andrew in "Brimstone and Treacle" was rather overdone. "Playing the Game," in which the toys confront Jane and Michael about their mistreatment, might be too scary for some children. I thought the best of the new songs was "Precision and Order" which revealed character without beating the audience over the head quite so much. The tendency to preachiness is, alas, a significant flaw in the show.
As for the performances, as I noted above, Gavin Lee was the standout. I was also quite impressed with Blythe Wilson as Mrs. Banks and Laird Mackintosh as Mr. Banks. The title character was played by Caroline Sheen and, while there was nothing wrong with her performance, Mary didn't seem to have a lot of personality.
All in all, this is reasonable family entertainment. It's nothing earth shattering, but it's not like people go to shows like that expecting major revolutions in the American theatre. The Disney folks have always succeeded by understanding their target market and this is no exception.