Brian, first off, thanks for hanging in there even after the first couple of posts flaming you pretty hard. You've definitely purchased an outstanding camera that will take a bit to get used to it. I don't shoot a lot of auto sports but I shoot a ton of wildlife and have used a Canon 20D, 5D, a Nikon D90 and now the Pentax K-7. You are going to find a couple of things that are a bit finicky with the Pentax, mainly high ISO performance and Continuous Autofocus.
The high ISO is manageable if you can remember to optimize the settings for your shooting conditions. I mainly try to use faster glass rather than cranking up the ISO if at all possible. I assume you're shooting for around 1/250th or faster with your shots to avoid subject blur? I wouldn't shoot at anything less than around ISO 400 for sports (I shoot a bit of bull riding which is about as crazy as you can get and I never shoot less than ISO 400).
For autofocus, the faster the lenses, the faster your camera is going to perform. Sigma has some nice tele's for the Pentax and from what I understand the Pentax 55-300mm is okay as well. Pentax's DA* glass is fairly pricey but top of the line, especially their 60-250mm DA* and 300mm DA*. I have decent success with Continuous AF but I wouldn't say that Pentax cameras are really designed to speed demons. The engineers err on the side of AF accuracy rather than speed and I can attest that I get more "keepers" with the Pentax but have to work harder to get them. As a reference point, I throw out around 25-33% of my Nikon D90 panning shots because the camera missed focus.
Stick with the central AF point or select another one manually if you want to keep the subject off-center. Don't rely on AF-Auto selection. Not many cameras out there can really beat the Central AF point for accuracy.
I hope this helps. Stick with the K-7 and I think you'll be very pleased with the results. I find it produces some of the punchiest, high-quality photos I can get with a mid-level DSLR. I like the RAW output much better than my Nikon D90. You just have to think about the metering and AF a tiny bit more on Pentax. I guess that's because Pentax shooters can be trusted to be a bit brighter than the average Canikon shooter.