What is the big thing in the announcements that could be considered exciting? You'll be able to make money from your creations.
As an XNA Creator Club premium member you'll be able to submit your games to the service, set a price point for your games (between 200 and 800 Microsoft Points), and after a peer review your game will be available to download by millions of game players on Xbox LIVE. Every quarter, you'll receive a payment for up to 70% of all money your game has earned. People will be able to play a trial of your game before they buy it as well.
I remember what seems like forever ago now. I was sitting in my office trying to convince people that you could use managed code to make games. That it was feasible to run managed code and make a good game on a console as well as Windows. I remember the reluctance people had in believing that. Now look today. Have you seen Schizoid? A game that has been released and making money. Now we have this announcement today. Almost anyone has the potential to make money by writing a game and getting it on the service. It couldn't be simpler.
As for me, I'm celebrating this announcement by taking a trip to Vegas. (Ok, that's just coincidence, but still).