I looked at getting a Merc C350e or whatever it's called. It advertised 25-30 miles on battery. However, most of the forums seem to say you're lucky if you get half that - 12 miles is typical in summer, less than 10 miles in winter. So good enough to go to the shops and back, but not really much use if you're doing regular trips more than 50 miles.
I was looking at ones about 5 years old. Trouble is the battery warranty is 6 years, and plenty seemed to be failing at about the 5 year mark, so buying a second hand one at that age is a big gamble. If the battery fails outside of warranty, then you're looking at a big repair bill. And worse, in some circumstances the damn thing won't even start/run on the petrol engine if the battery is FUBAR. And you lose boot space because the battery has to live somewhere.
Buying/Leasing/NeverNevering one new might be an option, but I'd be looking to get rid after 3-4 years so that it's still got some residual value in the battery warranty. All this tech is too new for real reliability figures to be known once the car is 5 years old.