The other day I saw someone posted something about a rumored SX30 IS replacing the SX20 IS. One difference mentioned as a possibility was switching to a LiIon system. Kind of surprised me but it would make sense for Canon to have a reason to raise the price (battery, plus charger to start, and a demand for extra batteries).
Some people imply that if an SX30 IS replaces the SX20 IS, then a LiIon cell would be an improvement over the current 4xAA set-up.
One person I know was interested in an SX, but when she found out it used AA cells, that was a deal breaker for her (although she needs to keep a supply of some sort of AA cells for an EX flash she added after buying a Rebel).
Apologies if this has been gone over before...but I did use the search function and didn't find anything.