Nope, it isn't how hard you ride in NYC. While I can do a steady 20+mph on an open road with no problem on my roadie, it just isn't safe to do so riding the bike lane on 1st or 2nd Avenue in Manhattan. And then as I mentioned there are the traffic lights, probably the real limiting factor. Somewhere on this thread I posted how I beat my usual time by about 10 minutes, and that was because I made most of the lights, a very unusual occurrence, and that was on my usual mtb commuter too. Effort wise it was the same as usual.