Thanks for the link to nycopendata. There is a plethora of interesting NYC geospatial data there that I was unaware of.

Isn't building footprint included in the PLUTO corpus? Does nycopendata provide better building outlines?

You're right, there's something else called MapPLUTO: http://www.nyc.gov/html/dcp/html/bytes/applbyte.shtml that seems to include building footprints. My bet is they're from the same source.

MapPLUTO's footprints aren't for the buildings, but rather the boundaries of the property. It's a big shapefile for each borough. Totally worth exploring. It's got an insanely detailed metadata breakdown that explains a ton of the eccentricities.

As for the dates, most are guesses. If you plot the dates, you see they're overwhelmingly years that end in 0.

Right. That's what I was using when I was playing with the pluto data in openGl. Unfortunately/Fortunately some of you other programmers are much better than me at displaying this stuff in web apps.