For me it is the availability of charging to fit in with my lifestyle, so if petrol stations stocked fully charged exchange batteries that simply slid into place at one end of the car and were of universal size and fitment (maybe 2 or 3 sizes/specs would be needed to suit all applications) and just charged you for the amount of power used on the battery being swapped in, it would be far better.
They do this on Fluence taxis in Holland and it seems to work well, but the system to change power packs is complex and needs expensive hardware.
A combination of more charging points, more fast charging and the possibility of power pack swaps on demand would see me back in the EV circuit.
As the tech is fairly new, it would be best to standardise all chargers, plugs, socket etc and design interchangeable power packs-and then design the next range around these packs; eg pack size 1: Twizy and similar 2: ZOE and similar 3: Fluence, Leaf, Prius and similar. A simple slide in unit and connectors which fits into the rear bumper and had retractable wheels to move it would be easy to design. It would also need some security to stop it being stolen and would be useful if it could be removed completely and wheeled into the house, office, flat etc to charge it and keep it warm in the winter. This would open up the market to potential EV owners who live in a flat or have on street parking and nowhere to charge at home too.
To take it further, BH could include all charging from the points and exchange units in one easy monthly payment by using a BH card.
What is needed is a strong visionary of EV who can get manufacturers to all use the same pack styles and standardise everything, now, at this early stage.
It will be years before EVs are a true mainstream alternative to conv fuel cars, but quicker if they implemented these ideas now. Once a new EV is available at the same cost as standard cars if you factor in fuel and BH and can be used as simply, the market will take off.