First a question: Why did you link to the old version of the deck? I spent the first 5 minutes looking over the old version thinking up feedback before I realized that I should be looking at the other one.
Second, while I'm the one imsully is noting about the need for versatility , I have to agree with him that you need consistency. If you cannot put at least 2x of a card, it's likely not worth it or had better not be an integral part of your plan. For example, if you're running a vampire deck and throw in a copy of Exquisite Blood as a 1x just for grins, that's fine, but if it's potentially important to your strategy, it NEEDS to be at least 2x if not more. This will both increase the consistency but also will make the deck easier to learn to play, as you don't have to sit and figure everything out from scratch all the time.
I'm also going to go one step further than imsully to say that I really think the deck is lacking in direction and would likely get wiped out pretty quickly at an FNM (I don't mean to be harsh). Of course there is likely to be variation in the meta at each LGS, but I'm just not seeing the power play here. If you want to do a crazy blue/white spirit deck, run it, but at current there are a lot of pieces that aren't fitting in.
Here are a few questions/comments/suggestions:
1) Jace's Phantasm - I understand the pull toward including a possible one-drop 5/5 flyer, but I'm not seeing any mill elements here. So were you just planning on waiting until they have 10 cards via spells or casualties from combat/removal? If that's the case, you might as well be waiting to hard-cast Avacyn.
2) Serra Avenger - again, a nice, tempting card, but those spots could be better utilized with either spirit creatures (there are quite a few of them), spells to pull Lingering Souls out of the graveyard (Archaeomancer or better in your case Runic Repetition), or some sort of removal, i.e., Oblivion Ring.
3) Blade Splicer - same story here. You're making tokens, so that's good, but those tokens aren't playing into the strength of the deck. Why not go with 2x more Drogskol Captain to ensure the spirits are that much stronger?
4) Mirran Crusader - I would sideboard him. He doesn't fit the scheme, doesn't have flying, and his protections only work in some instances. You could easily use those spots to either include additional Phyrexian Metamorphs or something else to that end.
5) You're splashing black just for one Unburial Rites? If it's an Avacyn casting strategy, why not just run Defy Death? It might cost one more, but it's in a primary color AND would give her two +1/+1s.
6) Why not just run 3x Ponder?
7) Take or leave this one - personally I like Divine Reckoning over Day of Judgment. Same cost, but you can maintain a creature advantage if you have the biggest one, AND it has flashback, giving you double the board clears for the same number of slots in the deck.
8) Why Spectral Flight when most of your creatures are already flying? You could take advantage of Favorable Winds and pump all those spirits even more. If you're looking for a pump enchantment, Spirit Mantle is still standard legal and gives your guy both +1/+1 and protection from creatures (not a bad deal there). Others that would better serve you are there.
9) The sideboard needs some work here, but I'll leave that up to you to figure out as you're more familiar with the decks your opponents are more likely to be running.
Then you can simplify your land base in a way that it will be much more consistent. I think there's a lot of promise here and it could be pulled together without spending too much or putting forth too much effort. Soon you'll be pumping lots of spirit tokens that can dive in for plenty of flying damage. Confetti will stream from the rafters, music will be playing, etc., etc.