Saw it 2nite. I could give a long review, but NovaPSULuvr and jjsocrates did a pretty good job.
It's a little confusing at first, in that it bounces back and forth between two stories: Brian's issues with his dad and his band mates in his early days, and Brian's issues with Dr. Eugene Landy in his later years. It takes a little bit of time to get comfortable with the story technique, but once you do the constant juxtapositions make sense.
Paul Dano absolutely nails the young Brian. John Cusack does a nice job as the older Brian, but the movie would have been better served with an actor that you wouldn't recognize.
Jake Abel looks very much like Mike Love, and plays him to a T. Paul Giamatti does a great job as Dr. Eugene Landy.
Elizabeth Banks deserves special mention for her performance as Melinda Ledbetter. To answer the earlier post, she's 41, and is absolutely smoking. (What would you expect from a lady that was a Tri Delt in college?) She's super easy on the eyes, and very convincing in her role.
I think it helps if you have some knowledge about Brian Wilson, or about the Beach Boys, before entering the theatre.
And I'd concur with a couple of folks that mentioned the recording scenes from the Pet Sounds record -- they were excellent.
And to avoid the flag, below is a pic of Elizabeth Banks.
I'd give it 3 out of 4 stars, meaning it's a movie I would recommend to family and friends.