Rates are reasonable, insurance is available (only $15 per day), they've got a diverse rental fleet with new machines, and the customer service was stellar from the booking of the reservation through turning in the bike.
These guys helped coordinate transportation to/from the airport including pick-up from the bus stop. They provided saddlebags & a tankbag for free. They got me in/out quickly with minimal paperwork. They offer discounts on gear for renters. They've got motorcycle specific detailed route maps for many of the best rides in northern Cali. They have a pretty liberal cancellation policy w/ full refund 72 hours out. On top of all this they are in the heart of some of the best roads in the US.
http://www.rentasportbike.com/