Firstly, let me say I've mostly used a K-x for the last year (almost), and the K-r for 1 day.
- High ISO is a smidgen better on the K-r. In low light setting ISO 12800 is still barely usable IMO
- In lowish tungsten light, AF is
crap on the K-r, you'd do better to turn the lights off, and let the green AF lamp do its thing (which it does very well)
- Was shooting macros with DA 35 Limited, and I'm sure I saw shutter induced blur at 1/80 and 1/100. Did the K-r get the left-over K-7 shutters????
- In camera image handling is nowhere as fast or smooth in the K-r as compared to the K-x. Zooming in and out of an image in preview needs more optimisation (IMO)
IMO the focus issue is a biggy, especially if you are shooting in low light with a wide aperture (narrow DOF), the others are minor.
I'd like to see Falk test one for shutter-blur!
Hopefully, firmware updates might fix some of these issues.
When you do things right, IQ is pretty good.
(K-r ISO200 Tamron SP 90 F8 1/250 Hand held!)