If I were you, I would really pay attention to your mana curve. Also, with so many one or two copy cards, this deck will not play as consistently as you need it to. Balance your 1 and 2 cmc spells with your high end cmc cards.
As far as creatures go, you have some good ones but they vary far too much in ability and the point of your deck, outside of simple Vamp aggro, is lost in the shuffles per se. Find your best creatures with low to moderate cmc and play with 3 or 4 of them. I would definitely go with 4 Vampire Nighthawks, 4 Stromkirk Captains, and 3 or 4 Rakish Heirs to pump up other vamps.
Since most vamps get bonuses from their combat damage, you should focus the rest of the deck on removal and protecting creatures that help with removal such as Olivia Voldaren. I would put two of her in this deck. Mask of Avacyn to protect her.
The other thing you may want to consider is that the New Phyrexia Block is going to rotate out soon along with 2012. I am hoping RtR will have some good replacements for cards that rotate out although you might not need them if you choose wisely.
Good luck, and as always, have fun.