Looks fucking awesome! One of the things I was worried about seems to have been destroyed by this trailer. What I was very worried about, was the scale and sense of scope. That has always been well achieved in the first two games, but going open-world style, I had visions of Skyrim's tiny towns and it feeling like the whole country is just a glorified backyard. This trailer seems to sway me otherwise though. The environments look huge and well scaled, as does the city. Very happy to see that.
Music is awesome as well. Geralt's appearance is okay, though I assume it's subject to change. I know you can customize his appearance in-game, so like Witcher 2, as soon as I get the chance, that pony tail is coming out. Haha. As for the horse riding, it seems decent enough. I doubt any game will match Mount & Blade in horse riding, but this seems like a good enough effort.
All in all, pretty excited. I'm planning on playing the first two games, and reading the books, soon to get into the series again, as well as create a canon character of which to import into the third game.