I finally got to play this tonight! And sadly, it bombed pretty hard. Went 1-3.
If and when you can get the big enchantments out (Exquisite Blood, Feed the Pack, etc.) then they can be great. The problem is that the current meta, at least where I'm at is just way too incredibly fast.
The main problem is that there just weren't enough creatures staying in my hand, especially when I'm using them as an extra resource to draw cards and kill things. Blood Artist + Barter in Blood definitely stole the show though. Any time that you can get a couple artists out and then essentially kill four creatures, that is at least a 16 point life swing in your favor. I cleared more than a couple boards with back to back Barter in Bloods, but that also left my board empty.
The problem wasn't quite as much of the fact that there aren't enough creatures in the deck, but rather that they all cost so little and are rather insignificant in the grand scheme of things, that you end up committing a lot of them to the board very quickly. And when you do that, and then sacrifice a bunch, you end up with an empty hand and just top decking the rest of the game. With all the extra life gained from the Blood Artists, will definitely want to include a full set of Sign in Bloods. For the most part, the enchantments are definitely cool when they hit the field, and allowed me stall for a few more turns whenever they did, but they should probably be dropped almost entirely for something that will help out more immediately and more readily.
I am gonna have to say though, that I sided in a couple Gnaw to the Bones and they rock the house in this deck. Sack a bunch of creatures to get a life swing from the Blood Artists, and then gain twice that much life, and then do it again with flashback. Even if you have only 4 creatures in the graveyard, that is 16 life for 6 mana. Will probably be main boarding those from now on because you really need that extra stall factor here.
Champion of Lambholt was pretty useless, because you'd just end up wanting to sacrifice it anyway. Will definitely drop those. Craterhoof Behemoth was much the same way; you never had enough creatures on the board and enough mana to make it worth while.
Lastly, definitely need a bunch of enchantment and artifact hate in the sideboard, possibly main. Oblivion Ring shuts down your sacs. Witchbane Orb shuts down Blood Artist. And I'm sure there is plenty more where that came from.
Gaining from sacrificing and life gain are really the stars of the deck, and we definitely need to play more on that fact. A lot more.