I did it at the end of last year and enjoyed it. Great race, but tougher than I thought it was going to be. The bridges (especially Verrazano and Queensboro) are quite energy-sapping if you havent incorporated many hills in your training, the drag along 5th Ave towards Central Park is one long slope, and Central Park itself is just one rolling hill after another. The crowds through Brooklyn and along 1st Ave were superb, but The Bronx was probably one of my favourite parts, yet you only run through about a mile of it!
As already mentioned, take something warm and disposable to Staten Island for the start. You'll be there for a while and you will be exposed to the elements... and it could be very cold at 6.30am!
For me, one of the best parts was being in New York AFTER the race. No better place to celebrate your achievement.
Word of advice: wear your medal everywhere you go for about 2 days after the race and you'll get treated like royalty, from simple congratulations by friendly strangers, to discounts on meals!!