Great question! I really wanted to test that today so I did a lot of jumping across the field of view with the model and fast walking testing both the burst and clear of the buffer and the AF tracking. Using the 24-70 I would call it on par and slightly more accurate than the Canon 1DX. Very fast and accurate tracking, zero hunting even when the model was wearing an all black dress and a hit rate based on what I am seeing in the DNG files of about 97-98%.
Not really. While the K3 is faster in FPS, the K1 is at least twice as fast as clearing the buffer which frankly more than makes up for the difference as I don't have to stop as much to wait for the buffer. This was while shooting DNG to card1 and JPG to card 2
The 24-70 is sharp sharp sharp. I tried the K1 with firmware 0.48 and the 24-70 at a local Pentax pre production demo.
Images shot with the 24-70 were very sharp. Unfortunately Pentax has a policy at present of not allowing photographers who get to try the camera of posting full res images.
I think it would be best to wait for official firmware 1.0 reviews of production models or at least full res images.