dude.. kid me not
thats awsome!
but dont devalue your questions man, they're great
Have you already shot the interview by the way? (seems likely) if not, it'd be interesting to hear if Rx has made it into other places in the framework or if there are any plans on doing that. To hear those guys talk threading and sync would also be awsome 
Im actually planning to use Rx in a little project of mine linked to project natal (using a hypothetical api unfortunatly)
its a very good fit because natal, like any input device is like a hose of updates that im looking to use as input to make updates of my own. rx would significaly ease the writing of that code and also use fewer threads/tasks that are just waiting for something to happen.
Rx will also help the system be more provider agnostic, the input updates are just an observable of some type, it doesnt have to be a natal, it could be test code or webcams or whatever.
for now i guess i have to write the thing as a silverlight library since thats the only way to get at the Rx bits at the moment but hopefully .net4 beta2 is not to far away (and hopefully Rx is in beta2
)