I quite liked living in the Tenderloin. It's close to transit, it's cheap, and it's got great restaurants. I wouldn't live there if I had a cohabitating partner or kids, though.
During my year and a half there I had to wash poop off my shoe once. It took me a few minutes. My rent was several hundred dollars per month cheaper than any other place I lived in the Bay area. I'll wash anything off anything for a thousand dollars a minute.