If I could afford it. I can't. But I would. If you're doing biz at the NIH, this is the only way to roll. The shuttle will shoot you over there in a jif, and there'll be less hassle at the security gate than with a private vehicle. Still some hassle though. Expect delays.
As others have pointed out, it's an easy few blocks to the Metro. There are ample adequate restaurants in similarly easy walking distances, and a few really nice wine shops, too. It's possible to abandon your car for the entire stay and never feel a bit deprived.
Those traveling with kids might also appreciate that there is a coin-op laundry on site. Breakfast was varied and abundant, and the eatin' courtyard relaxing and peaceful. There is a Safeway right nearby for sundries you may have forgotten to pack. Staff is super helpful and courteous.