I was just wondering about these a while ago, and one question I still have is: If these are so great, why don't manufacurers use them OEM? I mean if you look at all the trouble they go through to make a bike lighter, would'nt a LiFePO4 battery be a no-brainer?
I thought the same thing and figured it's a mixture of cost (Shorais are something like $150+ vs conventional lead acid of ~$80) and not wanting to invest in the minor design/production changes that would be required for current product line. That said, I think it's only a matter of time before these things are standard in most production bikes because, as you said, the weight loss is pretty amazing (something like 9 lbs vs 2 lbs according to
here).