Vinod Khosla recently talked at the Energy Storage Association, and here is a good article about it.
There are a lot of interesting points, but the key take away to the sector was to lower the price. He completely dismissed the current tech in Li-ion batteries for the application. (And blatantly said A123 will not exist in 10yrs. ouch.) Khosla indicated "the bar for storage as round-trip efficiency better than that of lead-acid batteries with costs below $100 per kilowatt-hour."
Axion's PbC tech lowers lead-acid prices even further by allowing for increased cycles. It is only a matter of time, but Axion needs to do a better job at marketing itself to wall street.