Not great, but could be a lot worse. Crystal city is on two of the main subway lines. And has a Virigina regional rail and Amtrak stop. There is a pretty major bus depot there too.

The downside is one of the subway lines only runs every 13 minutes during rush hour. And that cannot be increased without decreasing runs on other lines (because they share a tunnel). Maybe Amazon will convince the governments to run more on that line (and take it away from the other lines).

edit: Forgot to mention that airport access is probably the best place in the entire country. You could basically walk to national airport.