A product that isnt available yet and a board that is 5x as expensive as an off the shelf mobo+cpu combo 5x (or more) the speed arent a great arguement that ppc is alive and kicking on the dektop. In the case of the Sam it suggests otherwise (ie., only so expensive because demand is so small). I mean no discredit to the people involved in the development of the above mentioned systems though, if I had the money to spend on new toys I'd actually like a Sam.
