The 2014 TCS NYC Marathon was my first NYC Marathon, and it was amazing.
From start to finish, it was an experience I will never forget.
The expo was great- it get a little crowded, but I didn't have to wait to pickup my bib and shirt. There are TONS of booths, and many give out free samples, plus you can pick up just about anything running related.
I opted to take the option of the bus from the public library straight to Staten Island, and from what I've heard that was definitely the way to go. You wait on one line and get right on a bus that delivers you to the start. You do wind up waiting a few hours though, so I suggest find a spot and camp out. Wear tons of layers to keep warm and maybe bring something to eat, read, listen to.
Once your section lines up though, then it's non stop. You will walk slowly to the start and once you cross the start, it's on. Staten Island goes by quickly. You're on the bridge a lot longer than you think, but it makes for great photo ops. Brooklyn has TONS of spirit and everyone comes out to cheer you on. Queens is great, but you're not by people for a lot of the borough- be weary of the 59th street bridge. It's more daunting than it appears. You're in Manhattan and then the Bronx for a very short while. Then you go back into Manhattan to the finish.
There are tons of photographers, and their aid stations are at every mile after 3. When you finish you get your medal, and photograph taken. Then you get a bag of snacks, a foil to keep warm, and a really nice poncho.
It's a class act from start to finish, and NYRR really makes sure its an experience you will never forget.