As a Steam gamer that won't be buying a console this gen or next I would be happy to pay MS a monthly fee to access a decent catalog of exclusive games. Put titles like Halo in the Win store and give me a couple freebies each month with membership and they will taking money right out of Valve's pocket.
I know most PC gamers don't like the idea of a payed subscription but access to xbox exclusives, 20+ free games a year, and discounts for the price of a single new game is a good deal. I think I spend more than that annually on Steam games I never get around to playing.
im quite happy with the free games from origin and buying humble bundles (that usually are less than a months xbl subscription)