I parked there this morning at 5. Probably 10% of the lot occupied. January and February are generally pretty slow there, though I have not tried Presidents Weekend which could be a challenge with the other lots that have shut down. Shuttles run every 20 mins.
The shuttle does make a stop at Embassy Suites on the way to the airport.
When I looked at their web site a few days ago it indicated a jump to $15 on April 1. They did this a year ago at Christmas, but if that's going to be their new rate they'll probably be on the higher side.
Tom in Arlington, Virginia