Damn! Almost forgot.
It would be really useful if you can recharge Tesla cars by connecting two together via the (updated?) mobile charger- so called Vehicle To Vehicle or V2V.
Obviously this is only going to be available initially for those lucky enough to purchase two Teslas, and as the numbers of EVs grow then presumably we'll have to go through the EV equivalent of the BluRay/HD format war. But then, that's going to happen with any centralised battery-swap or commercial fast recharge stations anyway.
Still it would be a useful feature if Model S and the Roadster can recharge each other in an emergency.