Tyler Lockwood is a werewolf. Typically, werewolfs are described as "people" with big tempers. In the episode "The Turning Point" (I think) after Tyler and Jeremy kinda fight, the scene ends with Tyler walking away, but the camera is includes the full moon in the shot. I believe the is forshadowing for future events.
Personally, I think having werewolfs in Mystic Falls would assciate Vampire Diaries more with Twilight. So I don't like the idea of having werewolfs in Vampire Diaries. Although, interesting fact: There are vampires and werewolfs in Twilight, werewolfs and witches in Harry Potter, wheras Vampire Diaries has witches, vampires, and possibly even werewolfs.
What do you think? Is Tyler a werewolf? Is the whole Lockwood family hiding a secret? What do you think of werewolfs in Mystic Falls?