You must be overwhelmed by all the different opinions by nowSo, assuming that the two cameras do come in neck and neck, and
taking the fact that the K10 has in-camera IS, can someone give me
their opinion on going towards one camera or the other.
Apart from deciding on the key camera specific features, my best advice is to hold both cameras when K10D arrives, look through the viewfinder and give them a spin. You should be able to make a decision pretty quickly.
Do note that K10D does not have picture/scenery modes. But since you are an accomplished photographer, you don't need them. That's why I think you will be intrigued by the unique K10D control. The HyperProgram mode (Phil called it "genius") acts like 3 modes, Program-Tv-Av, in one, and you can freely switch between them in real time and no mode switching. The Sv sensitivity priority (you can set ISO in the control wheels) and TAv (auto ISO with set aperture/shutter speed) modes should also be useful to you (won't be surprised that they will be copied by others).
Reading specs and opinions is fine. But nothing beats handling one in real life.