This tour is a great way to see the city and also a lot of fun. It was a little daunting at first with all the paperwork and insurance stuff but when your out and about it is wonderful. I would recommend spending the extra money for the upgraded car and spend at least 2 hours driving around.
Fortunately, San Fran is a city worth getting lost in...but that's just what happened, the GPS didn't account for some construction/road closures and we ended up touring an area of very little interest. The map in the car was barely legible and no one ever told us there were different route options.