The Verge (great new tech site from the former editor of Engadget and cream of tech writers from all kinds of places) had a
liveblog. They have "story streams" with all the updates and different blog posts--here is the
Nook event story stream.
The differences from the NC? Upgraded screen; upgraded processor; slightly lighter and I think slightly thinner; better battery life; more memory (RAM and storage); new apps (NC will have some of those apps, too). These things are all easily understood from the press coverage that I have seen.
Looks like all of us who invested in Oberon covers for our Nook Colors will still be able to use them if we upgrade to the Nook Tablet. That is a good thing.