They don't look much different to most humans - a little more gaunt and sinister. I have a dark elf vampire. Evil as sin itself
Vampires get some resistance to normal weapons too, but not much. The benefits are improved stats (between +5 to +15 on most attributes, depending on the time between each feed) and extra skills. Having nighteye and detect living creatures on tap makes them the ultimate thieves/assasins. Being able to charm, silence/fear, and go invisible is also nice (all on top of your racial skills)