I think a key question, for us, should be how much does it cost to get a rating and how much effort is involved.
Check out this link to a short document here
Unfortunately, you have to register as a publisher with www.esrb.org/ to get any information about cost and processes.
Thinking about question 2 a little more, how can it know a piece of software is a game? It's an exe file and data...Windows wouldn't have a clue unless the app told it to check for a rating.
Does anyone have any technical details of how this mechanism is going to work in Vista? Also, how is the international issue going to be resolved. Isn't ESRB ratings USA only or is it Global now?
EDIT: I found this link -http://www.esrb.org/esrbratings_faqs.asp. It's worth a read.