Another idea...

I think you need more fliers, it's a sweet combo but you don't have any way to protect your levitation so I feel like you'll need something else to get your creatures in the air, but where I play everyone has something in their sideboard to deal with enchantments or artifacts they don't like. I think you could use some more Nightshade Peddlers in case of annoying creatures with reach or some such. Favorable winds is also a possibility. Another thing to consider is enchanting your opponent with Levitation (If thats possible?) then they can't block you no matter what keywords they have

P.S. Pauper is only commons so if you want to play pauper you'll need to reshape a few things

I'm sure you've realized by now that I like to cover myself from every angle which often takes away from the potency of the deck so if you like your build, keep it for sure, I just like to assume worst case scenario for almost everything, 3 levitations should be more than enough, I do love how cheap of a deck it is, especially if it works out well. I would suggest testing it against removal heavy decks so that you can tell if it could handle bad scenarios or not.

p.s. any updates on older decks? I'm curious about a couple of them

Geist Snatch only targets creature spells, so I don't see how it could be used to protect enchantments...

Anyway, I like the idea man, hope it works.  I don't really know much as far as Standard goes...most of my cards are from Mirrodin block and earlier.  While I do have some later stuff, I don't really know many of the newer cards that well.  Let me know how well it works when you get the deck finished man

I would also consider Hinterland Harbor in place of a few basic lands.  Looked it up, it's Standard-legal.  I know you're trying to avoid rares, but you could always swap it back out for basics if you do play Pauper.

Oh, I agree it would work, just not the way you intended it to

I'm definitely still wanting to keep this deck cheap (regardless of the Pauper status), although I would imagine it can be moved that way if need be (but it would come at the cost of the biggest combo as both Bower Passage and Levitation are uncommons, so not much point there).

So there is a LOT to respond to, so I'll try to move things in an orderly fashion.

Geist Snatch could be good to stop creatures with reach, but realistically, there aren't many of those out there to begin with and most of them are green.  To which point I could just soulbond deathtouch to whatever creature and swing until they have to block it, or just overwhelm them with all my "unblockable" creatures.

Gitaxian Probe and the other "pay two life rather than paying the mana cost" cards are marginal in my books.  The most of them end up helping your opponent or could simply be paid for (unless you're dealing with a card of a color not in your deck).  But for drawing cards, I'm pretty well covered with Tandem Lookout, Amass the Components, and Triumph of Ferocity.  Further, given that this deck, perhaps more so than most others I run, is going to need you to continue pressing your advantage early in the game, the thought of giving up even two life to an opponent could be a problem as I'd then have to keep more back on defense.

You hit the nail on the head with Tower Geist and given the number of Levitations in the deck, I'd rather run Aether Adept over Misthollow Griffin.  While it doesn't have the natural flying, the cheaper mana cost will help the flow of the deck, as, let's be honest, the only real reason to run either is to have the Unsummon.

Gryff Vanguard is a five-drop 3/2 flyer.  I'll already be drawing cards as I said above and for that cost you could easily score an Air Elemental or another comparably large creature. 

Soul Seizer could prove fun and I might look into that.  But for that cost, Mind Control achieves the same goal, is the same legality, and guarantees the creature claiming effect.

Favorable Winds is a good idea and I've put two of them in the deck.

All good ideas though and I definitely appreciate the feedback.  NullParameter, if you give it a go, let me know how it plays for you.

imsully, which decks were you curious for an update on?  Some of the ones I've posted on here for ideas I haven't actually put together yet (although I will in the next month or two), but I can give you an update on the ones I do have finished.

I went the other way with it and made it a WUG, all flier, spirit based deck.  Then I ran a bunch of Favorable Winds to help pump them.  Here it is.

Obviously, I went a bit more expensive because I used a bunch of cards that I have lying around, like a Phanstasmal Image and some dual lands, but those aren't necessarily required, just nice to have.  And you could probably run a mostly UG spirits deck, with a smaller splash of W (Avacyn's Pilgrim maybe) for some great support stuff like Drogskol Captain.  There's actually tons of spirits to work with and tweak things to your liking.

I threw in a Moonsilver Spear, because I just love that card way too much, and it provides extra fliers.  And I definitely took a play out of your book and used a full playset of Sheltering Words to help protect my creatures, and I actually put another playset of Ranger's Guile in my sideboard for that exact same reason, although I'm hoping that the Drogskol Captains mitigate the need for them.  I guess time will tell.  I'm hoping to throw it all together and bring it to the pre-release tomorrow for games in between official matches.

Let me know if you have any other ideas to add on.