Here's Reid Wilkes' post about his article in MSDN magazine on NGEN in Whidbey:
...and here's the article itself:
This is an EXCELLENT overview of what is new in NGEN in Whidbey.
Now that the cat's out of the bag, you can expect some more ngen related content from me in the near future. (In between bouts of Halo 2, I find time to do a bit of testing of NGEN)