I can't believe it's taken us this long to discover Bartlett's Bunkhouse, because we visit SF often, and it's an incredible value. Clean, efficient, close to virtually everything (an 8-minute walk to the Moscone Center and within a couple of blocks of Westfield and tons of shopping and delicious food), the amenities you NEED when traveling, and great customer service. The overhead light wasn't working when we checked in, and the guy at the front desk had it fixed in short order.
We especially liked the fact that we could come and go freely without bothering anyone, and there was a safe in the room.
Not a lot of frills, but the frills are unnecessary. The vibe is warm and friendly. Really enjoyed our stay here.