Some of these technologies are of no use to those of us that live in areas where the cost of energy is consistent all day and night and year round.
Part of that maybe the problem (no intelligence in the infrastructure). But in the meantime if I were to have solar or any other resource put up that would benefit from stored energy for later use, it'll throw the payback vs normal utility curve way off to where I'd have to live here for decades to get my money back in anything but smugness.
As far as LI battery technology, it seems that the Prius used NMhd batteries because the number of charge discharge cycles was greater, since the batteries in the story were expected to have a cycle per day, the owner would have to replace them realistically every 3-4 years.
As far as the greater energy content of LI batteries, that is a risk that is always present with batteries. As long as the controller / charger is smart and has a layer or two of fault checking, the risk of runaway thermal events is pretty low. (The problem people had with Lithium Ion AA cell batteries where they are available was when people put them into standard NiCad or NiMh chargers, which apply too much current too quickly and make them pop to start fires. Since this is an integrated system by Panasonic with no capacity to mix and match technology evident, I'd say the risks is low.)
It would be possible with standard deep cycle lead acid batteries, but than you have to have climate control for your batteries above and beyond that proposed, and than your dedicating a good chunk of floorspace to batteries (You can't stack them because of heat buildup when discharging). I know the Central Offices I've been in have had a good chunk of their floorspace dedicated to just power, and even than only for the few minutes it takes for the diesel to kick over .. and you don't want to know what happens to expensive telephone equipment when it starts getting fed progressive amounts lower than 48VDC.)