... Elon Musk has one hell of a rager over this. This could make electric cars that could go from Florida to New York on one charge, and recharge in similar time to a gas refill, a possibility.
Say you got 500 miles to a charge, which is a reasonable amount if these numbers are to be believed. That's the amount of miles driven by the average US driver in 2 weeks. So if the battery needs to be replaced after 8-10 charges, you're talking once a quarter. If the battery costs $250 and is easily user-replaceable, this isn't a big deal:
My quick, rough math says that if it lost 5% of the original maximum after every charge and the maximum charge of a brand new battery were 500 miles, 10 charges would come out to 3875 miles. If the battery can be produced for $250, that comes out to 15.5 miles to every $1 spent on the battery. Now, consider experiments are in progress to allow free/nearly free recharges, so the cost would really be reduced to just the battery. The current gas price I see out my window is $3.33/gal and my Scion xB gets about 30 MPG.
So, my Scion costs $3.33 to go 30 miles. The Tesla with a $250 battery would cost $2, and not explode the environment.