How does National Harbour rate as an incall location? Any input appreciated.

Thanks xxx Sweet Cassie

Try the exact opposite side of the beltway.

As far as I know it's allright. The Gaylord  is kind of expansive so there is more walking involved than others to get to your room. I believe parking is in a garage that also requires a short walk to the hotel.

it's not near anything, and not Metro accessible.

But if I had to guess most hobbyist drive their own vehicle, to the location when doing an incall.

I would stick with more well developed areas Cassie.
as has been pointed out no METRO, and getting there can be of tricky if your coming from VA and you havent tried exiting off the Beltway there before. (You have to get in the right lane in Virginia to make the exit!...which I didnt the first time I tried and getting there was and adventure I'd rather skip.)
Its near virtually nothing except the Beltway (oh for joy) and the Potomac River...a bunch of commercial buildings not near anything else.
On the other hand, for guys in PG County or Old Town Alexandria it would beat treking into The District or out to Tysons.
With that in mind I think most providers would rather have a much larger population to draw from hense their attraction to DC and Tysons.
Hope this is of some help Cassie.

Might as well be in Richmond.  I would think the goal is to be somewhere that people routinely pass by to make the visit a simple detour.

Do that many people "pass by" National Harbor?