BED BUGS and DIRTY.
My wife got 82 bites in 1 night. We were on the 6th floor. We changed to teh 4th floor to a double room, and the shower had long hairs attached to the wall. Simply disgusting.
Yes, It is cheap, but not worth to stay on it if you can pay a little bit more for a safer place.
Location is very good for touristic attractions, although I think downtown of SF is the worst area of the city.