You make a very good point with the 911 option, that would be a very nice feature to have in case you were already on route to the hospital, or just out and about, and something causes a situation to become even worse, like in the case of someone all the sudden suffering from a heart attack or stroke. Also imagine driverless ambulance, with paramedics in the back, where the ambulance could signal to other cars wirelessly what route it's going to take to an emergency. Then cars either pull over or just reroute to continue on without getting in the way.
I would like to see speed limits done away with if speed is no longer a factor for safty, but I think you'd still have to consider fuel economy. The faster a vehicle travels the more fuel it has to consume. So there probably will still be some "fuel optimal" speed limit.
Just not having to worry about some crazy b*$%) who's doing her makeup on the highway on the way to work ramming into the side of my car, which has happens to me, is enough to sell me on driverless cars. I mean, she was passing me on a single lane highway doing 80Km/h with on coming traffic while putting on mascara. I looked over right at her and thought, this is it, I'm toast. I went off the shoulder of the road and took my foot off the gas while working hard not to tense up and keep the car going straight on the gravel shoulder while it slowed down, got out and promptly threw up. Luckily I got away with just a few scratches to my driver side, $2,700 to fix. Cops never caught her, I gave a description of her and the car, but was a little busy focusing on not dying to get her license plate. <== This is why we need driverless cars.