Go see this film!!! I think the reviews have been spot-on. A lot of people are saying it's Martin Scorsese's best film since Casino, but I think it was even better than that one. (Which I thought was good, but dragged on a bit in places) Lots of great tension in this film. Jack Nicholson was born to play this role. There's hardly anything I don't like him in, but he proved once again why he's the greatest living actor IMHO.
I'm not even a big Leo fan and he was great, too. Just an excellent cast that was very well directed. If Scorsese doesn't finally win an Oscar I'll be surprised.
The music was great as well - lots of Stones, "Sail on Sailor" by the Beach Boys," "Well Well Well" by John Lennon, some southern rock, Patsy Cline, etc. The music was very well placed, too. Jack even has a great line about John Lennon in the film.
Also I forgot to mention Van Morrison's version of "Comfortably Numb" from The Wall - Live in Berlin. Also used to great affect. Along with Cameron Crowe, I think Scorsese is one of the masters of music placement in flims.
I give it five stars!!!
And in the end...