KalKal
Superstar
I'm only Level 21 or 22 (in Hardcore, though), and fighting the Bloodseekers and the Vampire bosses in the 'Blood Harvest' zone IS pretty fun (and challenging the way they kind of "jump" you out of nowhere...you're just walking along then BAM! Boss fight!). And I haven't found any Scrolls of Escape or made and Death Evasion potions, so I'm playing without a safety net when the infamous Lag Monster comes after meSeason 2 is fukking crack right now.
Lvl 50 in ten hours, blowing up enemies as a Barbarian
The mount don't suck no mo
Loot pinata
Something that took a little while to dawn on me is that the "blood pact" system is kind of a step towards Runewords. Based on the way the slot into armor, I'm convinced that they're pointing towards a later season/expansion having D2 style Runewords.
I also like how one of the first vampire powers you get is essentially "Life Leech". Works great with Barbarian's Frenzy attack.