I just started going to PrimeDoc, which is a combined primary care/urgent care practice in the building across from Saks in Chevy Chase. They also have other locations.
https://primedoc.com/
I really like them! They seem to be a hybrid model: more geared to actual primary care than are the various urgent care chains around town, but they take walk-ins during certain hours. I'd planned to schedule a physical there but got sick in the meantime and was able to schedule an appointment online on very short notice (next day) even though I was not yet an established patient.
I saw Dr. Beryl Kompancaril and really liked her, as well as all the staff I dealt with.
I have CareFirst BCBS through the DC exchange and had no trouble with insurance. Visits and tests covered with the usual copay, no billing hassles, very user-friendly online portal.