Thinking that I would end up with the Westin Dulles Airport, I booked the 4* hotel shown with the same amenities (shuttle, fitness, pool, restaurant, business center, wi-fi) and ended up with the Sheraton Herndon Dulles hotel, for $80 (2/23/11-2/24/11). Each time I search again, the price appears to fluctuate from minute to minute - $73, $74, $79, $80 - but I'm guessing it's the same hotel.
