DustyB,
I suppose it is only marginal, but as every aircraft within 30 miles now has to be identified on radar, and ATC now knows who you are and where you are coming from, it may deter terrorists. You take off or enter the zone without an ADIZ and you are in big trouble.
PoetPilot,
Not sure about the Hudson corridor, I didn't see anything inthe NOTAMs against it, and we still see choppers moving up and down it.