Presently, I have about 1k mile(max) to go before I have to replace my OEM Yokos. I can tell a huge difference in the loss of traction on my current tires. (I think the cold weather have a part in the loss of traction as well.)
Cold weather has a HUGE impact on high-performance tires.
As the tread wears down, the tires generally feel pretty good on dry pavement (in warmer weather) but performance on wet roads declines.
It's amazing how much the OEM tires have an impact on NSX's handling performance.
Yes, the OEM tires are really great at that. Their precision in cornering is probably better than any other tire. The tire manufacturer can do a lot with designing a tire when they know which corner of the car it's going to be mounted on. See the FAQ for more info about the OEM tires.
Anyhow, should I stay with OEM tires?
If you like them, yes, definitely.
If so, how much are they and where can I get them without feeling like I got robbed?
Best prices you can get are to (a) join the NSX Club of America (
http://www.nsxca.org ) if you haven't done so already, and then (b) call the club's contacts at Discount Tire Direct for the wholesale prices they give to NSX Club members.
If you don't want to join the club, another place to check prices (you can do it on-line) is the Tire Rack at
http://www.tirerack.com They have a network of installers all over the country who can install them for you locally.