Just hook it to my veins!
Sorry, sorry. Trying to be objective here, but it's hard not get excited watching this 35 minute chunk of Witcher 3:Wild Hunt gameplay.
This video shows off a number of Witcher 3 locales and systems. It starts in a city big enough that you really need a horse to traverse it effectively and follows protagonist Geralt through his quest to investigate a childlike monster. It seems like this is the same, or similar to the, the extended demo that was shown at San Diego Comic-Con.
It's also long enough to constitute a spoiler, so be forewarned.