I think there are some differences...above all, Juliet. She's in love in two different ways, to me. In Shakespearean plays she's so in love, with really torment...while in the anime is something really sweet, and there isn't sooo much deep torment as in the play...
Romeo I'm still studying him... anyway also the other characters have to be considered deeper...
I love Willy character too! he's such a crazy person! i luv the idea of putting him in the play, and also the Romeo's pegasus, Cielo -that in Italian means sky-
...it's nice to see they tried their most to make a good work and make a lot of hints to Italian language-as the play, as u know, takes place in Veron.