Quite often, actually. I can remember a two-week streak last month when I never ate at home.
I guess its about 50/50 most of the time... I can never get too much of my favorite restaurants in the Seattle area like The Met, The Palisade, Dahlia Lounge, Dick's, Anthony's, Spuds on Alki, Gordon Biersch Brewery Restaurant (mmmmm), Cafe Starbucks (full service restaurant), Il Fornaio, Jazz Alley, Nordstrom (when I'm in the Nordstrom building and don't want to cross the skybridge to Cafe Starbucks-- good pizza, btw), oh the list goes on.
I prefer fine dining, but settle for fast food once in a while when I'm on the run (or in the South End...lol).