So, after using the K-1 for about a month now the improvements over my K-3 are very apparent. The resolution of the sensor is almost obscene at times, the detail level (even without pixel shift) just keeps blowing me away. After doing a couple of landscape shots with my newly acquired FA-35mm F/2 AL, I actually started diving into those photos....there are all these things going on in the frame I didn't see when taking the photo. Like the sample shot below (sized down). The people's silhouettes on the horizon are just tack sharp and even though taken against the sunset, no problem recovering the shadows filled with detail.
This is just an absolutely magnificent camera!