I had a wonderful two weeks staying at Mark and Sarah's place. The apartment was very clean and homely. My room was very spacious and felt more like a studio apartment rather than a room. Sarah was very attentive and quick to respond but at the same time I had plenty of privacy.
Potrero hill is a fantastic neighbourhood, very sunny, with plenty of great coffee shops and restaurants and incredible views over the city. There are several grocery stores right next to the house and the connections to the rest of San Francisco are convenient and easy.
I felt very much at home in Mark and Sarah's place and throughly enjoyed my stay. I will certainly come back :)