I've always wound up getting a cover, which changes all these fine-grained ergonomic considerations that people split hairs over. I tried to stick it out with a naked Kindle Touch (ergonomically it was fine, maybe not as good as Nook), but wound up eventually dinging up the screen a little bit (not even knowing how or when it happened). Now I have the lighted cover (it finally went on sale) and have been happy with that arrangement.
I don't know if my experience is typical, but it seems prudent to use a cover. In which case it doesn't matter as much how it feels in your hand without one. So I don't put much emphasis on that 'feature'.