I heard Vampirism follows the same pattern as it did in Oblivion. Meaning that you first contract the disease, with no real symptoms. After 48 hours without cure, you become a vampire. This works in stages: without feeding you become more powerful, but also it becomes more visible that you are a vampire. You will gradually be unable to walk in the sun, and people will shun you for your pale looks. If you feed, however, that process halts (and is even reverted?).
I assume that you'll be able to turn back normal somehow by means of a specific quest, though once that is complete, you'll become immune to vampirism.
For werewolves: I never found them very useful. There's a guy in the Compagnions, though, Vilkas, who in one quest seemed to be able to change form at will. Is this also possible for the player character? (In Morrowind/Bloodmoon there was a pendant that enabled switching)
