Let's do some math

Ok, math is hard, but how else are you going to figure out if this car is good for YOU?

Nissan sees the capability for dramatic user cost-savings versus a traditional internal-combustion equivalent.

Using my Jetta as a baseline...
I get about 26MPG in mixed driving (city+highway). I generally put in about 11 gallons a week after having driven about 286 miles (for an average of 40.85 miles per day).

11 gallons per week @ $2.90 per gallon == $31.9, or $4.55 per day to operate.
but, if gas goes up like it did last year...
11 gallons per week @ $3.90 per gallon == $42.9, or $6.12 per day to operate.

Charging the Leaf...
Let's go crazy, and say it takes a full 16 hours to charge at 110volts, 15A.
Anything that plugs into 110v shouldn't draw any more than 15 amps, so that's a safe bet.
16 hr charge on a standard 110V 15A circuit would only deliver about 26kWh
Dan Neil, accomplished car reviewer for the LA Times, reports the battery stories 24 kwh.
24kWh @ 0.13 per kWh == $3.12 per day to operate

So, using the low end of the gas scale == $4.50 per day * 365 days == $1642.50 per year.
And figuring electricity at the high-end of the scale (all my charging would be at night, when rates are typically lower) == $3.12 per day * 365 == $1138.80

$503.7 cheaper in the first year.

Unfortuantely, if the car itself is $10,000 more expensive that a normal small car, it would take almost 20 years for the savings to make a difference, so Nissan had better keep the price point low enough for it make a difference. Of course, here's where that government rebate of potentially $7500 could make a huge difference in the car saving me money before the first 5 years are up. Also consider, no oil changes or other service required.

So rather than trying to do math about MPG, which is like trying to compare apples to oranges, let's compare WHAT REALLY COUNTS -- dollars per mile. Because in the end, that's what's really important -- how much it will cost you to run this car.

On the plus side:
* Electricity is cheaper than gasoline (assuming that gas costs $2.50 or more a gallon)
* A fully electric car will not need oil changes
* Plug it in when you get home

On the negative side:
* Limited range
* Will take a long time to recharge
* Sooner or later, batteries will need to be replaced ($$$)