I've got the MTB version of the Northwaves too, and am very happy with them (especially as I got them almost half price).
Size: I've got reasonably broad feet (it was always a G fitting when I had them measured as a kid), normally take a 43 in shoes, and am happy in a Northwave 43 (also for Shimano and Pearl Izumi, though my Bontrager shoes are 44).
Picking up on SP's point re cleat fitting, the slots are about half a cm further forward than on my Pearl Izumi shoes and Exustar sandals, and about the same position as my Bonty shoes.