I liked the main quest as a story, but it didn't suit an open-world game at all, barely giving you any suitable spots for side-questing. The main quest in the base game wasn't perfect in this regard either, but at least it usually allowed you to walk from one place to another on your own, whereas B&W usually didn't even give you the option. The endgame was the most ridiculous, sending you all over the map from one cutscene to another with these "a few days later" gaps in between, never letting you do anything on your own. I suppose that in terms of the story it's appropriate that you finish the main quest rather quickly and then just stay around to improve your vineyard and search for random witcher's work, but after finishing the main quest I'm way overleveled for all the side quests I've found so far, so it's hardly perfect that way either.
I agree with
Yoshiyyahu that some of the quests in the main storyline were a bit convoluted, even though the quests themselves were really cool. Getting a couple of obscure tasks to gather a bunch of super-rare ingredients for some magic concoction was especially lazy. It didn't really feel like you were doing any actual detective work on your own, because it was just a linear romp where things somehow solved themselves in a cutscene.
There was very little in terms of C&C from what I could tell, but the fork near the end was cool and better than I initially assumed.
I got the Empress ending (the best and correct one, in my opinion) on my playthrough of the main game in this save, yet Ciri came to Corvo Bianco telling about her witchering adventures. Bug or feature? Kind of sucks if they're treating the witcher ending as canon regardless of your choices.
The mutations are a nice addition to character development, even if you don't get to play with them that much (not until NG+, at least). Totally overpowered, but it's nice that you get some use out of all of the thousands of spare mutagens you've picked up.
Having a few quests revolve around visiting points of interest might be kind of lazy, but I do appreciate the effort to tie them more logically into the game world. All in all, I'd say the world-building is notably better than in the base game in almost every way.
