It's a whole bunch of little things. The dialogue, the way the PoV character thinks, the way the character explains things directly that would have been referenced more obliquely and more smoothly in previous books ... it's just not the same. And I like it less and less the more I re-read it...

You're right that he explains things much more directly and not nearly as smoothly as RJ, but I'm hoping this is because he feels it necessary to recap stuff from previous books, at least early on. I remember reading one of his blog posts where he mentioned he was doing too much of this, and when Harriet pointed it out to him he tried to cut back, so maybe that element disappears as the book goes on.