When Zipcar gets a hold of Google's self-driving cars, then you won't even have to wait around at the recharging stations. You can just jump into the next available fully-charged car, and off you go. With a reservation, the entire route could be automatically planned ahead of time with railroad-esque precision. You heard it here first!

Depends on where you're going and what you're carrying.

Family of four with a baby or two, and a trunk / roof rack full of luggage? Transferring between cars would be a bit of a PITA. I'd opt for the swappable battery in that case (or a liquid-fueled vehicle).