We have been doing lithium for about 18 months now with no real problems. We have previously been testing them with the University here in Bath for about a year before we launched them on to the market. We had several different types of batteries that were tested and opted for the one we use now for a couple of reasons, one being it doesn't require a battery management system and the other being it gives a greater range to the others we tested. On the Uk road, I would say there are close to 500 Powabykes using the lithium battery.
I'll be honest will you, I'm not that technically minded so I couldn't comment on the various discharch curves and rates etc... sorry!