First a disclaimer - I'm not selling for Nissan or getting a kickback. I have no leasing experience either.
Now I'm glad to have bought a 2012. Given however the big upgrades coming to the 2013, a 39 month (Three and a quarter year) lease has some pros. This is a $3K down ( most elderly trade in cars would cover this ) and a $289 base model lease price. I would lease the base model.
Add $40 in electric a month and you are running. Now you have 39 months of electric driving for under $350 a month (with maintenance) and you can look at buying one of the improved EV's in 2016's model year. Admittedly you loose the payments but if prices fall - the purchase of a 2016 could be quite a bit cheaper.
Three years of improvement in model years. Given all the Nissan upgrades each year in the Leaf and all the competition coming on line - could be sweet.
Folks experienced at leases feel free to discuss the down sides.