There is interest in several forums about how the K10D body compares to the K100D. Here are a series of photos that show both bodies side-by-side, with and without the K10D battery grip. These are personal photos that I took very quickly this morning, and I did not spend any time on the lighting, etc. However, I think they will give folks a general idea of the overall size and ergonomics of the K10D relative to the K100D (and previous *ist series cameras). Hope these photos are of help until you have a chance to hold the K10D for yourself.
I've heard some folks lament that the K10D is much bigger than the K100D. Obviously how a camera's size, weight and balance "feels" in your hand is a personal matter, and that's why it's so important to spend time handling an slr before buying it. Yes, the K10D body is approximately 3/8" wider and 3/8" taller than the K100D. However, most people who have held it will likely comment that it has a compact yet solid feel to it. And, even with the battery grip it still feels lighter and more manageable than other high-end slrs I have owned. I've added two photos at the end of this post that compare the K10D (with battery grip) next to my EOS 1D-MkII. Of course, these two cameras are targeted to two entirely different shooters. However, I think one perspective in viewing the K10D is not to immediately compare how much bigger it is versus an entry-level type of body (K100D), but how much smaller it is versus higher performance and more expensive bodies that offer advanced features including weather sealing.