I've seen a few threads to the same effect, but 3G service is abysmal in NYC and has been since I purchased my iPhone. I have been thinking of upgrading, but as a long time Verizon Wireless customer I'm completely fed up with the poor performance. My wife has the same phone with AT&T, and the speeds just blow Verizon away.
In fact, I've done all of these things repeatedly over the last few months with zero results. This is the fasted test result over the last few days. Pathetic.