You might also want to consider the Hyatt Dulles. They have a free shuttle to to IAD and it's an all-suites hotel. Their rates are usually competitive with the other airport hotels. I've stayed there a couple of times when I've had very early or very late flights and it was fine. The sitting area in the suite is in the same room as the bed, but it's a decent size and it's nice to have a little extra room.

I've had breakfast in the restaurant and the food was good (we ordered off the menu, so can't comment on the buffet). I haven't had lunch or dinner there, but did have afternoon room service and it was fine. There is also a separate bar next to the restaurant.

They also have a pool and an exercise room if that's important.