The deal is that I pay $10 a month and can use any of their fleet of cars around the city for $12 an hour (I get one free hour an month), with the hours of 11:00pm to 7:00am counted as one hour. That cost covers just about everything, including insurance and petrol.
There's one just up the road from me at work (about 500 meters away), so using them when I'm at work will be easy.
The nearest one to home is about a 10 minute tram ride away, so it won't be too bad if I need to use one during "normal hours", but if I want to use one outside of when the trams are running (which I see as being likely) it will be about a half hour walk.
Of course, if I decide to use it frequently, I can upgrade my account and end up paying less per hour, with a $50, $100 and $200 plan giving a 5%, 10% and 20% on the hiring fee respectively.
So, it should be interesting. If anyone else decides to join, let them know I recommended you, as that gives both of us 3 free hours driving. :)