Adding my two cents, a little late: I'm in NYC, also. Last winter was my first being really hardcore about commuting to work on my bike as much as possible (4.5 miles each way Upper West to Midtown). There was loads of snow and ice, with patches of ice and black ice for what seemed like weeks at a time. I was running fixed gear (for the first time, DOH!) with some cheap 700x32 PerformanceBike Forte Gotham tires. Riding fixed was fun, but I missed my single-speed freewheel pretty quickly, when I realized I couldn't coast through ruts or otherwise stop the pedals when I needed to. I made pedal contact with deep snow and ice "rocks" many times before the end of the season. Grip-wise, there was lots of slip-sliding around in the slush and snow, with a couple of good falls when I hit some invisibly smooth ice patches (luckily, the worst was in Riverside Park, when I hit a patch going pretty fast that had me slammed to the ground and sliding 15-20 feet before I came to stop and realized what had happened). My whole body was often sore from using all my muscles just to keep the bike upright.

I'd say the greenways are not cleared nearly as well as the streets are, and where we cyclists are forced to ride on the streets is usually full of packed plowed snow, slush, or black ice for as long as it takes to melt after a good snow storm.

Last winter did seem to be out of the norm, so I'm still trying to decide if I should go with a full studded tire this time around or just a nice lightweight cyclocross tire. Those Land Cruisers are interesting, but I'm looking at the Panaracer CG CX. I live in a small studio with my wifey, so I've got only one bike to work with. I do have an extra set of wheels (that I'm supposed to get rid of, because there's no room) that I may outfit with studded tires, to save them for quick swaps when the weather changes.