I felt that vampirism in Oblivion was tedious, unfriendly and not much different in terms of power than your average pc. Now feeding means nothing to vampire as that was the case in Morrowind. Vampire grows stronger by 4 levels as they grow older, these levels are: Young, Adult, Old, Ancient Vampire. Vampires now are powerful but also get powers to help them become overlords of night such as Vampire Speed and Vampire Jump. Vampire Blood Infusion to help in fight where you ignite your blood to heal your wounds. As you become vampire you need to be very careful as sun will turn you to ash in seconds...literaly. When you grow to become old and strong you will be able to increasingly resist Meridia influence that burns you trough sunlight, Young Vampires may want to remain in caves, and only travel at night, they also get minor regeneration which also grows in power. An Ancient Vampire will be able to walk in clear daylight with minor sunburn which is the effect of their good regeneration and resistance to Meridia influence. Vampires don't grow weaker, they don't need to feed and even if they did, it will change nothing. Ancient Vampires are considered powerful monsters and due to that have vastly reduced charisma. Should they wish to talk with a mortal, they will need to use their charm ability, or use magic to make them look handsome/beautiful.