Bit the bullet and got my K-5 this week. Amazing camera, coming from a k200d it's a whole new world to me.
I noticed one thing I haven't seen on the k200d: with flash mounted and a zoom lens (notably the Sigma 17-70) in Av mode, the camera automatically increases the shutter speed as the lens is zoomed to a greater focal length, and decreases it as the lens is zoomed out.
As if it somehow tries to compensate for camera shake - somewhat odd with flash and SR in place, though.
Yet so far, the camera simply leaves me in awe, and such little details only improve on the general picture