Harvey Keitel is also excellent in it as Sport. In fact even the minor parts like Andy the gun salesmen, Peter Boyle and the other taxi drivers and Scorsese as the jealous, demented husband fantasising about killing his cheating wife are superb.
But there are at least 5 Scorsese flicks i prefer to it and i doubt i'd ever watch it again as it's one of those films that you watch and love as a moody teenager but grow out as you reach adulthood.