1. clearly, you've never shot sports or high-action events
by decoupling the AF function from the shutter button, you can choose when to focus and when to not focus (such as in the case with pre-set focus) and switch seamlessly in between the two in a pinch. It also helps that the camera doesn't annoyingly refocus every time you want to take a picture
2. this i could agree with. I much prefer the way this is handled on canikon bodies I've used before (5d, d700, d3, etc) where the selection of points is done by multi-controller-stick-thing. With this, I could just leave it on multipoint AF mode and simply press the stick down to go back to center focusing or use the stick to move around the focusing point. unfortunately, there's no menu option you can use to fix this
aside from the af point selection though, i find everything else about the k-5's ergonomics to be near-perfect
edit: @ eulogy - you can program the shutter's DoF preview to give you an optical preview. this is actually what i have it set to on my camera, the RAW button on my k-5 is used as the digital preview instead