I never liked the change that Dawnguard made to level 4 vampirism. You get the message that you are a blood starved vampire that is hated by all but nothing changes. Now if I forget to feed and my vampire reaches level 4 and I see that message, I immediately change to vampire lord form and feed on anyone around me regardless where I am. I see it as denying the hunger for to long and releasing the beast. I do something similar with my werewolf character. I wear the cursed ring of Hircine so the lycanthrophy feels like a real curse.