Suppose it is progress, it will probably be a better battery but wouldn't a new battery be better if somehow it was backward compatible... at least usable in the Pens. Perhaps it is... Does any one know? I have an E5 which uses a new battery .. At least usable in the e3 whilst I had it. Travelling with my family with a whole range of olympus DSLRs would mean that we would need 5 different chargers!