I've clocked nearly 60 hours in the game, and am sitting at 37% with the Velen and Novigrad main quests complete. I haven't touched the Island yet. But I think I've seen enough to comment on the game as a whole. Despite my earlier complaints about the UI and some of the controls (which still annoy me) I do thoroughly enjoy it.
I have to give major props to CDPR, the story is probably one of the most compelling I've ever experienced in a video game. I am a fervent "games are not movies" purist, I often deride the "story" in games like Mass Effect because I don't think cramming a movie into your video game is not how you are supposed to tell stories in the medium. On the surface this is what the Witcher 3 is, but it is done so masterfully I can't help but be sucked in.
I am not exactly sure what it is, but I think a major part of the reason it works is the ambiguity of the world, the characters, and the decisions you make. You don't really know what is going to happen; everyone has an agenda, everyone is trying to use Geralt, and everyone lies constantly. You get some truths, some half-truths, and some outright lies, without always being able to tell which is which. You get thrust into conflicts between evils and you really aren't sure who is the lesser one you should side with. And often you are put in situations where no outcome is better than the other, they both just really suck. This texture paints the world in such a way that your disbelief is utterly suspended allowing for a high level of emotional engagement.
The Witcher shows the benefit of not having an "alignment points" system that many RPGs contain (which I generally dislike as well). It allows you to make choices based on the context of the situation and the personality of your "Geralt" without affecting parts of the game that aren't your story (no spamming "paragon" because that is your build).
They also have some extremely talented voice actors. Whomever did the Baron (Edit:
James Clyde) is an absolute star, that is some of the best acting I've ever seen just about anywhere. That guy should get an award for his portrayal of such a complex and conflicted character.
As an aside, Ciri is fucking awesome. I really wish I could play the game as her instead (as long as they fixed her run/walk animation). Maybe she will become a playable character in the expansions?