I think this is not worth 3 whole stars, but it is in a great location and it was clean, but very dated and noisy. Almost worse than the outside traffic is the noise from the bathroom vent! The vent went on automatically with the bathroom light, and the light switch was on a wall 3 feet away from the bathroom door. It's fine if you are by yourself or if you don't have to use the bathroom at night!
Probably the three best things about the Carl are the price, the location and free wi-fi! We walked a lot: to all the attractions in the Golden Gate Park, the Haight-Ashbury area, and "restaurant row" on 9th St.
There was adequate drawer space for a short stay, but hanging clothes went on a rack on the wall. The bed was comfortable.
Not sure if we'd go back. Oh, no internet from the office; could not communicate with them beforehand except by phone, so no written confirmation. Also unable to print out boarding passes before leaving for the airport.