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.
Public transit to Crystal City is about as good as it gets. Which is good, because the road traffic sucks.
Even with all that it’s one of the better transit systems in the US. Not as good as Chicago or NY, but for the size of city it’s good.
In any event it's generally minimally acceptable at best. Dumping a ton of people onto it will not help matters.
[1] https://www.aboutlawsuits.com/dc-metro-crash-lawsuit-filed-4... [2] https://fivethirtyeight.com/features/washington-d-c-s-metro-...
I ride Metro every week day (bus + train) and look: I'm still alive! And on time almost every day. I much prefer it to driving.