as of mine, I remember stepping outside of a tomb near seyda neen, and finding a small red box on right-down side of my HUD.
its said prolific (sort of) hemofilia. its said to have a +5 (or +1) bonus on fatigue, so i think its okay.
three days later, i strolling down the road west of ghost gate, and i feel like i just needed a rest, so i sleep.
to my suprise, this message box appear, says "you dream of a blood maiden..." and my character was changed into a cool looking undead.
my health begin to drop because of the sunlight, and because i still didnt realize the full effect of it, i hit the rest button again, sleep for 6 hours hoping
i'll wake at the dusk...
and i just roast my first vampire to dust!!!
ohh, the blessing of ignorance.. such a good experience.
(oh, and tell me if i should post this in spoiler thread instead )