First, let me make it clear that I didn't stay here, so I apologise if this skews the property rankings but I felt I needed to review the proprietor, Barbara, with whom I spoke today.
I called to enquire about a stay in July 2014, but there were no free apartments for the time I needed. Barbara gave me the very best customer service I've ever experienced, despite not being able to provide me with a place to stay. When I asked instead for some assistance in navigating and avoiding the unsafe parts of SF, she spent over 20 mins to answer each question I had and describe to me in great detail the parts of town that are ideal and the parts of town that were unsuitable for my needs, and even went so far as to suggest specific places I might enquire elsewhere.
I know SF is a wonderful place (it's why I'm coming to visit!), but within SF (as with any major city) there are some places which uninitiated tourists (like me) would do best to avoid, or at least be mindful of at particular times of day. I was terribly confused by various forums on the internet as to the boundaries of particular areas, and the apparent fact that one block can be perfectly safe at all hours, whereas the next might not be. She was honest with me about some of the not so nice parts of a city she clearly adores, and invited me to call back at any time if I had additional questions. She is an absolute superstar and I commend her.