I have my own car so I have never been compelled to use Autolib. I have never fully understood who their target customer might be. Even at 9€/30 min period, it seems a bit pricey to use one just to go shopping at IKEA or Carrefour and then they have very little cargo space. For shorter distances, the métro or a bus seems a lot more efficient.
Whatever the rational, they seem to be expanding the concept.