I'd agree on ditching the Olympus.
Between the Sony and the Pentax, well, you know I'm going to say the Pentax. But here are three good reasons why:
1. Excellent image quality when shooting RAW + surprisingly good high-ISO quality for its class.
2. Takes AA rechargeable batteries--Sanyo Eneloops ftw, and you can always use some lithiums in an emergency.
3. An incredible back catalog of super cheap manual focus lenses of extremely high quality. If you're on a budget, this is huge.
The K-m also has a better viewfinder (slightly), uses SDHC vs. the A200's CF card (personal preference here), and has the best kit lens in its class in terms of IQ. The DA 50-200 is also surprisingly good for a kit.
That said, the price difference is big (and kinda strange given the Sony had the higher MSRP).
You can talk to Taavi (EST) if you want more info about the K-m. I've got the K-x, which has the same body, and I think the ergonomics are just fine. It's a small camera, but it feels good in the hand.