We emitted 350 fewer lbs of carbon dioxide versus the previous vehicle. That's based on PSE's current load mix (32% coal, 36% hydro, 30% natural gas). Given current prices, it's likely that PSE will be using more natural gas and renewables, and less coal in the future, so things should only get better.
We don't get a separate electric bill for the LEAF, so it's a little hard to determine precisely what the actual costs have been. Using the 225 KWh reported by Carwings and a rate of $0.11 per KWh, figure around $25 for the month. By way of comparison, if we had been driving our Toyota Echo instead, we would have used 30 gallons of gasoline, at $3.30 per gallon, for a total of $100.
Which brings me to my final point. During the month we've had the LEAF, electric rates have gone from $0.11 per KWh to $0.11 per KWh. Electric rates are controlled by the utility commission. Local gasoline prices have gone from $3.20 per gallon to $3.45 per gallon. Gasoline prices fluctuate based on supply and demand, market speculation, unrest in the Middle East, and hurricanes in the Gulf of Mexico. I don't know about you, but I like knowing what my transportation costs are going to be more than a few days in advance.