I just received my new 70-200 2.8 IS II a few days ago, and I can say it is quite a bit more stiff and not as smooth compared to the zoom ring on my well-used 70-200 2.8 IS Ver I that I just sold. Mine isn't significant enough for me to be concerned, but it is a noticeable difference from my previous model. I expect that's just bc its new and it'll get smoother with a bit of use.
Edit: I didn't mean to imply mine is gritty at all, and I suppose the lack of "smoothness" comes from it taking considerably more effort to turn the zoom ring on the new lens vs my old one. I could turn the old one using just my thumb with little effort. Not so much on the new one.