I did a lot of experementing when i first got the camera, and this is what I found.
Color mode III, and saturation + for maximum vividness in the color. I love cold blue light (hot, actually, at 6800k), and I still like the effect these two settings give me. I was suprised to read that ken rockwell uses the same settings.
I only remove tone compensation from auto when i've got absolute and total control over my lighting, which is when i put it at +2. This creates a ton of range in very evenly lit photos, and provides a huge amount of depth. The downside is that the tiniest shadow becomes pitch black, so the lighting has to be pedantic and your subject very still. I find the results highly pleasing and worth the effort.
Alternatively, if you're having problems exposing a photo and things are washing out/blacking out, -2 will make the picture absolutely flat, but capture all the detail. It wil be the most boring photo you've ever seen, though.
Otherwise, I leave it on auto. There's too much change even in the same lighting conditions to take spur of the moment, naturally lit photos.