Mitch (PM on the XNA team) has been doing a bunch of writing lately it seems - not on his blog, but on the XNA team blog. His latest post:
gives a nice summary of the goals, layers and features of the XNA framework.
Even if you don't have the attention span to read the entire post, skip down to the "Wrap Up" section at the end. Here he gives a sample of XNA code to create a simple "game" - all it does is show a blue screen (and by that I mean a screen that is blue, not a blue screen ^_^).
This is the first XNA code made available and notice that you don't have to write your own game loop! Yea!