It's not the subject matter that I dislike. It's the art style and the trade dress.
I much prefer this:
To this:
I strongly dislike the cartoonish pseudo-3D rendering style of the latter and much prefer the more painterly style of the former.
I also dislike the new fonts they're using, and I much prefer the more fantasy-themed ripped banner than the weird red gradient bar with the cut-out edges that they're using for the new supplements.
I know, I know ... don't judge a book by its cover, but D&D's art has always had a big influence on my enthusiasm for the game. When I don't like the art, it does actually make me want to play the game less. And I already have reservations about the revised game's content so ...
I'm honestly teetering on the edge of the 5e band wagon here. This cover art isn't gonna push me off, no. But it is yet another little nudge closer to the edge. I think the now-delayed Eberron book's content is going to be the make-or-break point for me.