Being a new K-30 owner, I wanted to give it a try for one of the hardest sports to shoot: basketball in a dimly lit gym.
To do so I shot a few games the past few days of local summer basketball league for my news website. These players are a combination of high school, former community college and smaller college stars, all the way up to Division One athletes and players playing professionally in the Europe. The speed and explosiveness of these players takes some getting used to, and you really have to stay focused and know how to anticipate the action to get good shots (I'm still getting better at this.)
To aid me in my experiment, I also rented the very nice Sigma 70-200 EXII f/2.8 with the very quick HSM motor. The HSM motor is very quick by the way, and a great combo with the K-30. I've never really shot with Canon or Nikon, especially their higher end lenses, but the autofocus to me for this combo was very quick and very snappy. Any mistakes or missed shots were more on me than on the camera IMO. I also brought my DA*16-50 which also performed well, and I actually ended up using that more than the 70-200 to capture more of the action near the basket.
Speaking of user error, it took me about a game and a half to figure out the settings on the K-30 in a way that wouldn't cost me shots. I settled on Expanded AF (very handy) + selectable point AF + Continuous Focus + Continuous Focus Priority set to FPS over accuracy. I struggled in the beginning before I found this combo but after I hit that I was getting a lot of keepers.
As for whether the K-30 was better for the K-5 for this type of shooting, I haven't done a scientific test or anything but I would concur with deadwolfbones that the K-30 AF is snappier, more sure of itself. It reminds me a little of my PZ-1P in the way that it snaps into focus and stays there.
Could I have used the K-5 for this shooting, too? Yes. In fact, I did. I was very pleased with the K-30's performance, though, considering the light also wasn't the greatest, especially for being a mid-entry level camera.
Note: I'm not a spray and pray shooter, and I don't think the K-30 would be good for this type of style. If the K-3 comes out with a big buffer and improves on the ground made with the K-30, though, I could see that being a genuinely good sports shooting camera.
A few photos: