I drove to NYC last year to drop a friend off and really didn't have much trouble with the traffic.  People were pretty good about letting others merge, and even in Manhattan getting around wasn't really that difficult.  Honestly I have had far worse experiences driving in Pittsburgh's rush hour traffic than New Yorks.  In Pittsburgh if you kill a merge into a crowded lane because you simply have to chances are you will get someone giving you the finger and another person honking at you.  As long as you drive calmly and courteously in NY then everything seems to work out fine for the most part.