Lots of comment on the AF system....I am not a sports or action shooter so I have no useful input and trust others are more qualified in this area to make a judgment.
I can tell my personal story, which is very important and meaningful to me. I mainly shoot with a 50-500 Bigma...currently the latest HSM OS version. I have been a Bigma shooter for around 10 years. In that time I have gone from the DS to most of the other flagship models and now to the K1.
All previous models were a nightmare at AF in one way or another. Gaining focus lock in a crowded scene with a bird/squirrel in the brush was near impossible. Even in good conditions, focus lock was slow and the big ol' slow Bigma might hunt forever before locking focus...if it ever did. Many hundreds of shots were missed....maybe thousands over the years. I chalked it up to the Bigma being long and slow...even the new model exhibited the same problems unless in very good light.
So I get my new K1 and immediately mount my most used lens...the Bigma. I set it to Cop Mode for the best advantage at long shooting.....most is at 500mm. What happened next was simply amazing to me. It locked focus instantly, in every circumstance, almost every time and even in very low light. I found it unbelievable, but it was real and it still is. It does no hunting...none, it locks on the subject and you have your shot immediately.
Birds are mostly jittery, they don't linger as you take a coffee break while your Bigma gains focus lock. Case in point here...this Jay showed up and I knew from his appearance he was not going to stick around for more than a few seconds. The Bigma was mounted and ready on my desk, but in the past I would not have bothered ......knowing he would be gone before I could lock on focus. Not so with the K1...I picked it up, turned it on, focus was instantaneous and I fired.
So for me the K1 is a dream come true. It does everything I had only dreamed of and a lot more. My camera is for me and my use as I use it......I am fully and completely satisfied with the K1 and the AF system....as well as the SR, WB and wonderful color rendering.
My regrets to those that are not, but if you are a mostly a still shooter this camera is a Pentax miracle.
Old Norm once wrote an article of education regarding the AF systems on various cameras. The bottom line was that you can get most anything you want if you are willing to pay the price. At the price of the K1 we are getting a tremendous bargain.....you want more......open your wallet and spend the bucks, it's all out there but not at a K1 price.
Best Regards!