I would definitely stay here again.
Karl was very informative and responsive. Easy check-in/out (but do note it is the *downstairs* apartment B). It's about 20 min walk to the convention center or to the H street area. 10ish min to Metro. Never felt unsafe walking back late at night. Street parking nearby. Apartment was nice, had everything we needed and more. Good WiFi. Air conditioning was nice during a particularly hot, humid week. Whole apartment for the price of a hotel room, good deal.
My only minor complaints would be that the bathtub drained slowly and filled up a bit during a shower, and there was noise from upstairs neighbors walking around and street noise in the front bedroom.