Have never been much of a fan of proprietary batteries, leaves me at the mercy of the manufacturer and their willingness to support the product down the road.
I have been holding off on upgrade, my main thing was the inability to turn off noise reduction in the K20, not so much the battery type.
Now, with K-7, supposedly, the NR can be disabled AND it can be operated with just the AA`s in the grip,
( go lithium's
). (I know i read it somewhere, that it can be operated with AA`s alone). This most likely will be my next new camera.
And, yes , AA rechargeable lithium`s are available. You just have to sign a liability waiver that releases manufacturer from responsibility, when you burn your house down,
.
Cheers. Mike.