Basically, this deck either pumps your creatures for monstrous aggro or it mills your opponent to death. Being a mill deck, in my experience, most players now are taken by surprise and their sideboards oftentimes don't have anything to answer mill.
The best thing I love about Mill Decks is that they can rob your opponent of cards they want before they're even cast, and with this deck also functioning as an Aggro Deck, it won't lose to aggressive decks. (Though more creature control cards should be added when facing Weenie Swarm Decks.)
Plus, isn't it fun to tell your opponent, "Did you forget your Deck?" after you milled all of his/her cards?
Note: The only reason Glimpse the Unthinkable isn't in this deck is because of its price tag. :(
UPDATES:
12-16-13
-1 Island
-1 Swamp
-2 Memory Sluice
+2 Nephalia Drownyard
+2 Essence Harvest
12-19-13
-1 Mind Grind
-1 Mirko Vosk, Mind Drinker
-4 Death's Approach
+2 Jace, Memory Adept
+4 Dismember
1-12-14
-2 Essence Harvest
-1 Nephalia Drownyard
-1 Consuming Aberration
-2 Island
-2 Swamp
+2 Mana Leak
+4 Underground River
+2 Memory Sluice
1-26-14
-2 Memory Sluice
-2 Mana Leak
-1 Wight of Precinct Six
-1 Mind Grind
+4 Hedron Crab
+1 Trade Routes
+1 Nephalia Drownyard
2-1-14
-1 Trade Routes
-1 Island
-1 Wight of Precinct Six
+2 Surgical Extraction
+1 Oboro, Palace in the Clouds
Like most decks, the first few turns define this deck. If you don't mill your opponent quickly, it'll be hard to catch up. Fortunately, we have Augur of Bolas and Visions of Beyond (which also helps you tremendously in Mid-Late Game).
Main Deck Card Comments / Special Mentions:
Augur of Bolas deserves a special mention. In Early Game, it fetches you a badly needed mill spell and also doubles as a nice beefy blocker. Even towards the later parts of the game, it's still good.
Visions of Beyond, in my opinion, makes the deck. Without it, the deck's consistency dwindles after the first few turns. Being able to cantrip if badly needed, and later be an Ancestral Recall (one of the Power Nine) after using three mill spells is too good to pass up. Without it, you're sure to be holding 1 or less cards by Mid-Late Game. Update: I'm thinking of switching two Visions for two Phyrexian Arenas for a mosre stable draw engine that will undoubtedly helpful for a mill deck.
Jace's Phantasm is the best creature in the deck. A one to cast 5/5 Flying after casting two mill spells is incredible in any part of the game. It has incredible synergy with Nighthowler and can win games with it.
Dismember replaced Death's Approach as the removal card of the deck. It's just more efficient and not graveyard reliant like DA. Paying 4 Life is nothing and being able to pay for it for Mana instead of sacrificing Life is nice too. Being an Instant now helps Augur of Bolas more now that he has 22 possible targets.
Consuming Aberration is one of the deck's finishers. Once summoned, it becomes a gigantic monster (I once had it to 39/39) but that's not the best thing about it. It's true it may not have evasion of any kind but its second ability is far too good to miss out. Every time you cast a Spell (any spell), your opponent mills until he/she mills a Land. Combined with Visions of Beyond, Death's Approach, late Jace's Phantasms, and even your other mill spells, it will certainly finish up your opponent's deck or severely drain it of the cards your opponent wants to draw.
Nephalia Drownyard is an awesome land. It's uncounterable mill and uses excess mana to mill. The only bad thing about it is that it only produces colorless mana which can leave me Mana screwed for a few turns. One copy is enough to prevent being mana screwed. Update: Due to the sheer number of dual lands I now have, having two is reassuring especially in late game.
Jace, Memory Adept offers the option of milling 10 cards or giving me a draw, and with that, I feel that it is better than Mind Grind and Mirko Vosk, and is more consistent.
Hedron Crab is an amazing creature I overlooked. Trying him out made my Mind Sculpts into Glimpses and having two or more out is devastating to the opponent!
Trade Routes is an enchantment that doesn't need to be tapped to use so having one is fine since they don't really benefit me by having more copies out on the field. Comboing it with two or more Hedron Crabs allows me to mill the opponent even when I don't have lands in my hand since it'll allow me to bounce them back up. It also functions as a nice little draw engine.
Removed from Main Deck:
Nighthowler and his Bestow ability are often used with Jace's Phantasm to inflict major amounts of damage. He can also function as a beater/blocker (Wight of Precinct Six is more efficient) when needed.
Reason for Removing: 2 Black Mana symbols hurts versatility and promotes mana screwiness. Bestow is an awesome ability but with the problem of running into low creature count decks, it became this or Wight. Wight is faster by being two cmc and less mana clunky with its cost.
Essence Harvest is a finisher here. Though I just added it now (and is currently being tested), I believe that it will be a nice finisher or even a card that could save me when I'm running low on life.
Reason for Removing: It needs a creature on my side and with my recently lower creature count and its unreliability, it becomes a deadweight most of the time.
Sideboard:
Pithing Needle is used against Mill Hate cards like Tormod's Crypt and Elixir of Immortality.
AEtherize, Far // Away and Mutilate are used when dealing with creature heavy decks. Far // Away is better creature-centric decks that pump up a few creatures while Mutilate is sided in when facing Weenie Swarm Decks. AEtherize nullifies Token Decks and allows me to counterattack as well.
Telemin Performance is used for low creature count decks.
Maybeboard:
Artful Dodge for damage dealing, possibly to replace Annul(most likely) or Beckon Apparition in the Sideboard.
Crumbling Necropolis for a way to use Entering, possibly to replace 2 Islands and 2 Swamps in the Main Deck.
Gitaxian Probe for free cantrip, hand peek and deck thinning, possibly replacing Memory Sluice.
Surgical Extraction for disruption, probably gonna replace Memory Sluice or Gitaxian Probe.
Shelldock Isle for the added utility, will probably replace an Island.