Location. And nothing else.
I stayed at the Powell while attending a conference nearby. It didn't start well. And I really don't like to complain but....
The cab driver dropped us at the Cyril Magnin entrance where we were promptly greeted not by the hotel staff, but a few homeless people asking for money and giving us a hard time. When we got inside, check in was slow. I don't think the front desk had processed our internet reservation and they had to do both rooms all over from scratch - even though we had e-mail confirmation. 
The hallways weren't so bad. The building was dated, yes, but I enjoy an authentic antique feel and was looking forward to seeing my room. Unfortunately when I got there I found the carpet was terribly stained, the windows were wide open and the room was both frigid and humid (fog and rain all day...) and the bathroom had mould growing in between the tiles. I was in a suite and none of the clocks in the room had the correct time and neither remote control worked for the TV. About twenty minutes after I checked in a gentleman knocked on the door saying he had to take measurements of the room which made me slightly uncomfortable. Don't hotels have a turnaround time between 11 - 3 to take care of these things so as to not bother the guests?
I did sleep well and found the location to be a perfect base for shopping, dining and exploring (none of which I was able to do on this trip, sadly). I can tolerate a dated room, but unfortunately that along with poor housekeeping, maintenance and management will keep me from staying at The Powell when I do get to visit San Fran for pleasure.