Full electric cars are cool in my opinion, even the leaf. I did recently watch a documentary on the history of electric cars recently though which may have influenced my opinion.
Have you worked out how much it costs to do a full charge at home?
I like it, it's nippy and cheap to run. I haven't worked out the exact cost of a charge yet but it's about £2 from which I get between 60-90 miles. 
So, for a smallish car, that would cost around £10 in petrol or £7 in diesel.
How much per month is the battery rental?
Surely the batteries are included in the purchase price. Therefore my question would be......how much to replace the batteries and how long do they last?
The batteries are rented if you need them to be or, as Matt said, you can purchase. Either way, a price consideration.
Yeah, better to rent them, as that is cheaper than purchasing then buying more later when the current ones get feked.
5 year warranty on the battery.

Works out about the same cost wise for renting and purchasing (effect on the credit) but it makes a big difference to the resale value.