I'm in the same situation, but in just few days since I have IIs, not to many impressions.
First impression was that there is no difference, same size/weight, same viewfinder, same focus indoor, only buttons are little bit rearranged/moved, is not as simple and straightforward as k100d, press by accident some buttons.
But first shock was when I underexposed an image (meaning completely black, flash not fire), in Lightroom with +4ev and fill light I get the same image as an iso 400 correct exposured k100d image. Hope to have other shocks while using it in the next few...years. Anyway k100d a simple fit for purpose camera, pitty it has no liveview, and a large buffer.