Pentax is fine. They make good cameras. It's a bit like choosing between a Ford and a Chevy (or a Porche and a Ferrari), in the end it comes down to a matter of personal preference.

The advantage of Canon is a wider range of available lenses, the availability of full frame professional level bodies and the larger service organization with better pro support .

However you could make great images with either camera, so it's what feels best to you.

You have to ask in what ways does it "beat" the 5D II (or 7D). You can't reduce a camera to a number between 1 and 100. Well, you can because DxO do, but that number is pretty meaningless. It's like giving a similar numerical rating to a car based on 0-60 time, fuel economy, top speed and engine size and concluding the higher the number, the better the car.

It appears the K5 may have a higher dynamic range than the 5D II or 7D at lower ISO settings and it seems to have a slight noise advantage over ISO 6400, but in the region most used (100-3200) the 5D II seems to have lower noise (but the 7D has higher noise). Looks like a great camera, but we'll have to wait and see what reviews of a production model say about it.

If I was a Pentax system user, I's be happy to see it, but I don't see any Nikon or Canon system user switching to the Pentax system just to get a K5. It's not earth shattering and it's brand new, so it has a year of so lead on the 5D II and 7D. Wait another year and let's see what the 5D MkIII and 7D MkII can do. Basically it's foolish to get involved in chasing the "cutting edge" of technology because for 95% of users 95% of the time, you simply don't need or benefit from that last few percent performance increase that the latest cameras squeeze out.

Well looks like the 60D beats the K-5 in the detail department and even the D7000;)