I saw this two days ago at the New York Film Festival.
The plot: What happens when we acquire technology that allows us to migrate the boundary between dreams & reality, and what happens when that boundary blurs?
The Animation: Stunning; Madhouse always does good work and Kon's movies always produce some fun reality bending sequences.
The Music: Susumu Hirasawa who did the Paranoia Agent soundtrack came up with the score here too. The opening song is a particularly infectious number. It makes you smiley. It's like the opening song from Paranoia Agent on steroids. I really could not get the grin off my face till the beginning sequence ended.
The Cast: The voice cast is headed by Megumi Hayashibara, probably the most prolific and well known female seiyuu ever, with roles such as Rei Ayanami (Evangelion), Lina Inverse (Slayers), and Faye Valentine (Cowboy Bebop) to her credit. Akio Ohtsuka and Koichi Yamadera, Batou & Togusa of Ghost in the Shell fame, both play major roles as well. All do a fabulous job as usual, but Hayashibara really shines in her Paprika role.
This film has great animation, music & actors, but the plot is really just a thin veneer for the lucid dreaming sequences that permeate so much of Satoshi Kon's work. I still recommend seeing it because it's a really light fun film, but I don't think it adds up to being more than the sum of some really great parts. I think this one needs to be enjoyed in pieces rather than as a whole.