I recently handled the k100d and discovered to my surprise that the ae-lock and the e-dial are located on the back of the body right where the end of my right thumb rests. It almost feels like pentax forgot to leave a space for the thumb. I handled other entry level dlsr's at the store and most of them had similar problems, but to less of a degree. It seemed like the pentax placement of these two buttons make an accidental setting change possible. Of all the entry level cameras that I handled the rebel xt and xti's had the clearest area for the right thumb to rest. Other than the thumb issue, the k100d felt very comfortable in my hand. (But to my surprise, its grip design and size was very close to the rebel xt and xti's. Needless to say, the rebel xt and xti also felt comfortable for my hand, and made me wonder just how big the hands are of the reviewers who complain about the canon grip.)
However, my main concern is the placement of the dial and button being right under the end of my thumb. Could some of the owners of this camera please share their experience with handling the pentax k100d, since I am fairly sure I want to purchase one (when I compare it to the rebel, the pentax shake reduction stands out as the deciding feature). But my experience of holding the k100d is making me reconsider the rebel.