To be fair, I live in NYC and was at the Chelsea bombing. I also watched 9/11 from the river. There was indeed martial law in mine and the surrounding towns for the day during 9/11. Now I regularly see military patrolling 42nd street, armed. Also other places. I haven't seen any extra groups of men with high powered assault rifles in a day or two, but they roam the subways whenever some celebrity politician shows up, and the recent UN meetings saw streets that didn't belong to the UN cordoned off and just swarming with every alphabet agency out there. Should've taken a picture for you, Jeff.
I'm not throwing my opinion on either side, just sharing what I observe as witness.
I see your point - haven't been there (luckily!) at the moments of attacks, so I probably didn't see the full police operation that followed. My overall impression is that NYC is a city flooded by police and security at any time, not that it is specifically preparing for some thouroghly planned attack.
There are many things going on here, and especially as the elections are approaching, the security forces are multiplied, I think this is very expected.
But again, this is just my personal and uninformed opinion)