I ordered the K20D last Monday on Amazon and had it in my hands on Wednesday. It is heavier than the K100D and has a lot more buttons, that put all the features you want to use at your fingertips.
My camera had a bright white spot on the right hand side. A bunch of hot pixels. See pictures at
Flickr: MartinStein's stuff tagged with dust
I mentioned this to Amazons help and the told me to send it back within 30 days. A replacement was send immediately. Wow - very happy with Amazon.
I did not get the hot cluster on all pictures, but it did show up on the dust mapping screen - the camera can find dust on the sensor!
Compared to the K100D the mirror is much more quiet, and the speed the pictures are written to the SD card is amazing.