I looked at these before realising it would just be too small for my needs.
They do them with a range extender which is effectively a small petrol generator that charges the battery, this would go some way to overcome the fear of running out of juice but I don't think you would be able to do a really long journey using them.
I guess it comes down to your main reason for getting one - saving money or saving the planet. If saving money is the one, I am not convinced but that was looking at buying new.
FYI - I went with the Passat GTE - mainly to save money but that was via BIK rather than actual running costs. They are worth a look if you do lots of short journeys but still need a car for the occasional long trip.
I know there is a lot of talk about all cars moving to electricity but I am not convinced, can the national grid handle it??? The supply to my house needs upgrading if I want a charger larger than 3KWH.