Upper Market, North Beach, Hayes Valley, Valencia St, Mission Dolores, Polk Street, Upper Nob Hill, Haight Ashbury -- all fun locations.
I've lived near Dolores Park for the past 15 months now and have had a great experience. I've found community, made new friends, and have never felt unsafe whilst walking around at night.
We don't have highrise buildings or a thriving "downtown" like other urban cities, but we do have plenty of lively, energetic neighborhoods around the city and the best food & weather in the country.
I agree with the author that changes need to be made and that the homelessness problem is bad. But I think you can still have an overwhelmingly positive experience in the city if you pick one of the neighborhoods I mentioned above to live in.