RelayRides. Possible alternative to Zipcar?

At a recent Boston green festival at Government Center, I came across a new company, RelayRides.  They're a carsharing company/service that works sort of like Zipcar--you reserve a car online, pay a certain hourly rate, and drive.  The big difference is that RelayRides doesn't own the cars--they're owned by your neighbors.  In fact, if you own a car, you can join up and start renting out your car.  They provide the insurance.

Their web site is pretty detailed.  On the surface, it seems like a good model.  It's a way to make a lot of cars available for sharing, people who own cars get compensated, and the company makes some money but doesn't
have to own a zillion cars.




I know there are tool sharing and other kinds of sharing sites out there, but this car site is the first I've seen in the Boston area.

Has anyone out there tried this yet?  Let us know.