I rented a Beneteau 46 through them last summer, It was a simple process. I met the owner at his boat in San Francisco on the agreed upon date, where he walked me through his boats safety gear and operation. As far as the 35% I was on the renting side so it did not effect me. The owner seemed really happy his boat was getting used, and with the insurance provided for both the owner and myself including towing Boat US does not seem like much.
Anyway it worked out great and will be using the service in the future as it way cheaper than owning for me.