I may have to disagree with the general direction this thread is going.
I think nobody will argue that Canon and Nikon have a better AF system.
You do not need an 8000 dollar camera to reap the benefits. I have both the K10D and a Canon 20D. The Canon is far better in the AF department.
I also have the Bigma with a Canon mount. I am also aware that the Pentax variant does not have HSM. I have found that the Bigma with HSM is a delight to shoot. It is fast, predictable, and accurate. So much so that I often do not bother with continuous AF. I can shot birds in flight in single AF mode with no problems. This is all with a Canon 20D. I hear the 40D has improved AF over the 20 and 30D models. Not sure how much better though.
With the Pentax K10D, I do not have the Bigma, but I do have a Tamron 70-300mm lens. I have found a general minor difficulty in getting birds in flight. It is not just that the AF is noticeably slower, but its behaviour is not as good. I suppose if all I had was the K10D, I wouldn't notice it as much, but with the Canon alongside it...it is very noticeable just how different the performance level of the two actually are. This difference would still be there if you were to shoot a Canon XT or XTi. You do not need to focus on the pro level cameras to compare them to the Pentax bodies when it comes to AF.
With that said, the new DA* lenses have faster motors in the lens, so that will help in speeding up the mechanical sides of things. This does not help the software side of things however, and this is where I feel Pentax needs to focus more resources on, to remain competitive with sport and wildlife shooters.
Lets face it, you can manual focus anything and be very successful. Auto focus comes into its own if you’re shooting unpredictable fast moving objects however, as you may only have a few seconds to capture your subject. So although I love the K10D, when it is time to do wildlife, I always grab the 20D.
Some more examples taken with the 20D and Bigma. A collection of Gull shots.