I had a friend who attended, and I've known a few other musicians that attended. Be prepared for intense study, lots of theory, lots of performance, and recording. Most people I know that attended felt that it was beneficial to them....you will be exposed to lots of different styles of music and will have the opportunity to see some outstanding famous musicians perform and ask questions of them. Berkley also has an outstanding music department.
Good luck to you, and be sure to bone up on your theory before you apply as they have pre entrance requirements. There are no beginner courses there!