I use rechargeable batteries in Pentax K-x Digital SLR Camera and have now downloaded the new firmware so Pentax K-x Digital SLR Camera recognizes them faster. This is a must do because before I had to turn Pentax K-x Digital SLR Camera on and off and turn the live view on and off for it to recognize new batteries. I played with a few sets of batteries to make sure they would work. I’m saving the supplied lithium batteries to be a back up set when the rechargeable batteries get depleted.
The in camera shake reduction works with all my lenses including my old manual lenses from 30 years ago. The neat thing about using manual focus lenses (and wearing glasses like I do) with Pentax K-x Digital SLR Camera is that you can set Pentax K-x Digital SLR Camera to beep when you have focused the lens correctly, and there is also a visual indicator when you look thru the viewfinder. And every Pentax mount lens you buy will work with Pentax K-x Digital SLR Camera.