I used to like the look of this layout, but eventually I realized that, if you're actually going to be making serious use of the numpad, it was much better to have the numpad and arrow/navigation functions available at the same time than to have to toggle back and forth between the two using num lock. Some of PLUM's other experiments with the "compact keyboard with numpad" idea make a bit more sense to me, though they have their own problems...
Still, for those who like the layout but don't like (or can't get) PLUM or the CM TK, there are at least one or two other options out there...Reicat RX3 comes to mind.