We went on the San Fran tour on our first day in the city and it was absolutely fantastic. We couldn't believe how much of SF we saw (and learnt about) in two hours. Our guide, Alfred, was brilliant. Not only was he informative, we also laughed for the entire tour. (He is credit to your company! Thank you!)
For a great, enjoyable introduction to the city, we could not recommend this tour more! There are also some brilliant photo opportunities at Golden Gate Bridge that you would never get on one of the 'hop on hop off tours'.