They're interesting... My wife bought one, and after we finished with it we gave it to the local grade school for a student project for the 4th graders.
BTW - I have another reason for going low-power. Aside from noticing what the old tank cost, that is. I set the budget at 350 watts because that's what is left over on my 2KW generator after accounting for the furnace, fridge and freezer. I live well outside the village, and am the very last house on the DP&L power run. The houses further down the road are served by Edison. When there's an outage we're pretty low on the priority list (for good reason) and for the two years we've lived here have had 7 outages that lasted more than 5 hours. Ike knocked out power for 8 days for us, while Yellow Springs proper had power back in 2 days. I don't want to lose the tank because of a long outage!