One thing that is true of all lithium batteries is that if you're going to store them for awhile without using them, they have the best shelf life around 60% full. Not as useful for unexpected use that way, however.
Santa brought me the Sherpa 100ac- it's everything I expected, except for one thing- there's no 12V output, so I can't use my 12V ni-cad charger with it. But I've never actually used that option while camping, I have enough AA's and AAA's pre-charged that it's not an issue.