i really enjoy the ergonomics of the nook eink version, it had this slight concave on both sides so if your were holding it two handed it fit nice and snug around your fingers, and if holding it one handed it fell snug into your upper palm. couple that with the rubberized back and it's was really great to hold. Very well thought out device.
But of course once you buy a cover it's ergonomics goes out the window.