Hello Ian,
I have no experience whatsoever with the K20D... however, it has been reviewed quite well with respect to the Samsung sensor that Pentax has implemented. If I were not already invested in Canon mount glass (and a Canon DSLR body), I would seriously consider the K20D. Their viewfinders are supposed to be large and nice, while the sensor itself provides a nice balance of resolution and high iso performance.
Do you have any K20D photo samples (or insights) that you would like to share?