I'm sure everyone writes superlative reviews, so I'm going to mention some specifics:
QUIET: situated on a side street, probably the quietest place I've slept in a long time!
KITCHEN: well stocked with spices, condiments, and other staples so that you can start cooking here right away!
NEIGHBORHOOD: quiet street, but very close to Castro, Duboce Triangle, and Mission bars, restaurants, and stores
RESPONSE: Guillermo responded promptly to all queries and concerns, a model host!
I recommend it without reservation.