The movie was ruined by the ending which made no sense. I won't spell out the problems in public in case some one hasn't seen it.
Not only was it long but apparently not long enough to make sense. Seemed like something was cut.
It was not up to Scorcese's standards and Nicholson was playing his standard lunatic.
Sadly, the film (especially first half) was better than the ending.
Since it's Scorsese I kept comparing it to GoodFellas. In GF he made you care about even the minor characters and what ultimately happened to them. In Departed, I cared less about each character as the film progressed.
I realize Jack Nicholson has made a handsome living playing himself for the better part of 30 years but in an ensemble cast it's distracting and ultimately hurts the film.