A couple things I noticed - Contrast Detect AF is now much faster - before it used to go beyond "in focus" focus to nearly the other end, before zooming back.
Now it only goes a bit past "in focus" then snaps back!
In phase-detect AF LV, when in AF-C, it no longer flips the mirror like 2 times to take a picture, only flips it once like it should.
I will update my wishlist thread.
https://www.pentaxforums.com/forums/pentax-dslr-discussion/79015-k-x-firmware-wishlist.html
As for batteries, my 5+ year old energizer 2650 batteries are red in auto mode but can take pictures, use LV, and video fine while staying red. When in NiMH mode, they are green.