I actually liked the way it was done in The Witcher - a perfectly calm village by night could turn in to one nasty place to be
It would certainly add to the immersion.
But it although means that if we get to become a vampire or a werewolf they have to make sure we don't feel like we "don't belong", for example some of the night creatures should be indifferent to vamps and weres or something similar, and both vampires and werewolves should see better in the dark, not with some crappy night vision effect but the night just has to seam not as dark for them, so I can enjoy the beauty of Skyrim even if I hardly ever see it it by day.