Just a comment that may help save you some frustration: Verify if you can that the bike you want to take is in working condition before you do your transaction.

On my first experience with Velib, I got a bike from the rack only to discover that its chain was off. Then I had to wait 5 minutes to get a different one.

Many Velib riders have taken to turning the saddles backwards on bikes that have chains off, flat tires, or other problems so that other riders as well as the Velib maintenance crew know there's a problem.