looking for first time experience ...

marriott site (and others) say on airport property but a shuttle is also mentioned. what's the walk?

I've never stayed there (I live by Dulles), but from memory of Dulles's layout, it is not something you easily could walk to.

As the crow flies, it's about 2000 feet (less than half mile), but because of the buildings, roads and parking lots, you cannot walk straight there, and you likely don't have the sidewalks to walk there safely at all, either.

Let's put it this way: I've not seen pedestrians outside of the parking lots, arrival and departure areas. It's not made to walk up or out of.

Just wait for the shuttle.

I agree...take the shuttle. The Marriott isn't onsite in terms of being "attached" to the airport terminal/s itself. Not only is the distance a little too far to be considered "walkable," there are no pedestrian crossings/sidewalks for you to take to the Marriott from the main terminal.

as others have said, the Marriott IS the closest hotel to the terminal but not within easy walking distance and there are other hotels close by which may rate better on Trip Advisor which also have shuttles.

I like Marriotts but I'm not sure I would stay in that one again...more like poor motel than anything else but haven't been in a couple of years so that may have changed.

I stayed at Hyatt Place North last time I flew out of Dulles. I will tell you that I am very picky with my hotel choices. I highly suggest you look into staying here. It must've been newly remodeled. The place was spotless, plasma tv in the room, great bed...the Virgin America flight crew stays here. We all rode the shuttle van together. The hotel also serves breakfast, and will keep your car.