Another NY'er here. My commute is from Brooklyn to Midtown Manhattan via the Manhattan Bridge. It is 9.5 miles of bike lanes on a 10 mile ride. The hills are small, the bridge being the biggest one. The traffic does move slowly on the streets, mostly. I was in Seattle for a week and found riding there, one of the "best" cycling cities to be pretty scary actually, and not from lack of familiarity. NYC has it beat.

I'm beginning to think that NY is one of the best cycling cities around with bike lanes everywhere in Manhattan and Brooklyn. The other boroughs aren't as well covered, but they're getting there.