OK. I'm essentially an amateur, dog and flower kind of photographer, who occasionally gets to go out and shoot cool stuff. I have had the K-1 for not quite two weeks, and I have been very busy with my day job so real opportunities have been limited.
I have had a K-3 since its release, and I reckon I have a pretty good handle on its capabilities. The K-1 is genuinely in another league - AF is much better, resolution is appreciably better, ergonomics are improved, viewfinder is bigger with better functionality (I love the spirit level and plumb line in the OVF), etc. What it boils down to is that my keeper rate is higher and the pictures are better. Really.
These are basically snapshots, but I think they illustrate the point.
Have a look at this in flickr, then download the full size jpeg and look into Sammy's right eye. Could I have done the same with my FA77 on the K-3 @ f/2.8 and ISO400 (as close to fully equivalent as I can get)? I don't think so.
Could I have done this with my DA15 on the K-3? Of course not, because f/2.8 would be the equivalent and that's impossible. And the edges would be mush. The DA14 @ f/2.8 would be closer, but I don't have that lens.
I don't have a K-3 II, so can't comment on the pixel shift shots from that camera, but download the full size jpeg from flickr again and tell me if that could be done with any camera below medium format.