I announced a few months ago that Steam's Big Picture mode would be available for BETA soon. Well, that soon is now! You can opt in to the Big Picture mode BETA through your steam client!
(Picture shamelessly screen grabbed from youtube video below)
I'm not going to ramble on here about it because there is a fantastic youtube video below that shows it in action. Also, the official page gives heaps of information on it too. What do you see as the pros and cons, will you be using it? Check it out for yourself and discuss what you think in our forums.