If it were an option, I would have given 4.5 stars.
The location was excellent for us - about 2.5 miles from Stanford, and in a separate unit behind the main house in a quiet neighborhood.
The mattress was extremely comfortable, the refrigerator was quiet, and there were many thoughtful touches (Brita filter pitcher, umbrella, iron & ironing board, extra towels, blanket, duvet covers, etc.). The room lighting was good, and the space was more accommodating than it appeared in the photos (places to put luggage and other belongings, an entire closet, shelves, etc.). For a small space, it was well-designed to not feel cramped. It was very quiet at night. The wifi was okay and although it took a long time of running the water to get it, there was plenty of hot water and good shower pressure.
Why I didn't give 5 stars:
1. Although the window had a blackout shade, the closed blinds over the window in the door let in a large amount of light, that shone directly onto the bed. The host did turn off the extremely bright outdoor lights at my request the second night, but a lot of light still entered from somewhere. This would not be a problem for people who can sleep with lights on.
2. There was a very strong smell of room spray (Febreze?). We left the window open the first night and all the next day, but the smell was still overwhelming the second night. Not a problem for people not bothered by strong scents.
3. The bed was oddly made up with a bottom sheet and a folded duvet for each side of the bed. Neither duvet was large enough to cover the bed. Because the temperature was in the 70s when we stayed there, even a single layer of the duvet was too hot. But because there was no top sheet, our only option was to remove the duvets from their covers and use the two covers as narrow top sheets -- which did not work very well. The arrangement would have been okay in colder weather.