I should mention that Maury Yeston's Broadway score is a lovely one, but even though the Broadway musical was based on a movie (Fellini's 8 1/2) I didn't quite see how it could be made into a movie. But I'd felt the same way about Chicago and that was successful. Rob Marshall took pretty much the same approach for Nine. That may be the limitations of his style - skimpily clothed production numbers and choreography based largely on pole dancing. (My tastes in choreography run more to the classical Broadway style of Jerome Robbins and Michael Kidd, by the way. The modern film choreography I like best comes from Bollywood.)
Anyway, the film was interesting but flawed. Part of the problem is that the role of young Guido was cut. Leaving out "The Bells of St. Sebastian" makes it more obscure why mid-life crisis Guido has such a problem with his relationships with women. Sophia Loren, as Guido's mother, is given pretty much nothing to work with, while Kate Hudson, as an American reporter, gets a new song ("Cinema Italiano") which I related to but hated musically. (The gist of it is why everybody would want to be in an Italian movie.) The other actresses were more impressive, especially Fergie as Saraghina and Judy Dench as Lilli. Marion Cotillard's acting (in the role of Luisa) was excellent, but I thought her performance of "My Husband Makes Movies" (one of my favorite songs from the musical) was weak and passionless. As for Daniel Day-Lewis as Guido, he was more convincing in the role than I expected.
A few reviews I saw wondered why so many women were throwing themselves at Guido. I can't speak for anyone else, but he drives around in a way cool car.
All in all, the movie is just about average. I'd probably have liked it less had I paid to see it and a lot less had I paid full price.