David's place has a terrific location right at the base of Sacre Coeur. It's also super-convenient for three different metro lines, so it's really easy to get around the city from his flat. Multiple groceries just around the corner, as it's a neighborhood where actual people live (vs just being a bunch of tourists) and it's a great place to stay.
The flat is simple and has all the necessities. It's just a great base for seeing Paris. The front room with a big glass door opening out to open space and trees on the Montmarte hill is particularly nice.