OK, I got my KatzEye, but I have reservations. Basically, all the M42s I threw at it, displayed severe (6-8mm) front focus:
This shot with Super-Takumar 50mm f1.4. The focus, according to the split prism and microprism collar, was dead on 0mm (I qudruple checked).
This is what it looked like in the view finder.
This was shot after focusing using Live View. No problemo.
I double checked installation, no problem. I've done these checks before, and my K20D body does not have a front focus problem.
Interestingly, AF works fine; I mount an AF lens (FA31lim and Sigma18-50 checked), and AF, and the pics come out perfectly. Of course, according to the KatzEye, it's way out of focus from the center :-p I'd always thought that AF was reliant on the screen, so this was a bit of a surprise.
Anyhow, I've contacted them and hope to find a resolution. I LOVELOVELOVE the screen itself; the ergonomics of it is just superb; bright, high contrast, just fantastic split prism and microprism.
If only they were accurate!!! :-p