I know people get on NYRR for the 2012 debacle with Hurricane Sandy, but leave that aside. I ran NYC in 2011 and it was an incredible experience. Yes, it starts in Statin Island, but it's painless to get there via Ferry and Shuttle Buses. You also have the first 2-3 miles to get your groove on running over into Brooklyn and you're welcomed with crowds that never thin out. It's a whole lot of party from there!! The fans are out there and it's a whole bunch of culture to boot. Plenty of aid stations along the way. Expect to have some hills in NYC (which you don't realize when you're casually walking around) and you hit all 5 boroughs. Central Park is rough at the end on the legs, so be warned

Expo: good size, lots of vendors and a huge amount of people to visit