The theory behind this deck is that Derevi's ability will synergize better when used to control lands rather than specific creatures. There are some exceptions, of course, and tapping/untapping creatures is always an option, but the deck is build such that you should curve out quickly and powerfully if you use Derevi to untap your own lands.
In this deck, lands such as Simic Growth Chamber actually ramp your mana rather than slowing you down, and enchantments such as Dawn's Reflection are effectively doubled.
When playing this deck, your first few turns should be devoted to fielding as many birds as possible. Derevi's passive scales with number of evasive attackers you control, and each bird contributes to your mana ramp. By the time you have 3-5 birds (this should happen quickly), you should switch focus to generating card advantage. This deck can greatly outpace removal if certain cards are timed correctly. A single coastal piracy or Bident of Thassa will continually refill your hand, allowing you to have reserves at all times in case of Wraths or other such tomfoolery. Next, most of the tribal or anthem effects such as Beastmaster Ascension or Coat of Arms should end the game quickly. Alternatively, Opposition or Glare of Subdual can be used to completely lock down opponents. When you have one of these enchantments on the field, simply swing with your fliers, have them untap each other rather than your lands, wait until your opponent's untap step, and tap whatever you deem most important.
Alternatively, if you are fighting a counter-heavy control deck, you can tap their lands rather than untapping your own, securing your post combat main faze casts. This slows your tempo a bit, but it's better than being countered.
The only true untap-abuse creature I included was Beguiler of Wills. The deck generates its own card advantage while maintaining aggro, so I judged that cards like Arcanis or Azami would not be worth their cost (in $, that is, if you already have them, feel free to include them). Beguiler, however, has incredible synergy with the rest of the deck. Your mana ramps so you can get her out ahead of removal. You field tons of creatures, enabling her ability. And finally, every single untap can target her, allowing you to essentially end the game if she gets past her summoning sickness.
Potential Weaknesses: If all opponents can field a single fat flier early and you do not have any anthem effects or means to lock them down, it can prevent you from swinging freely with Derevi, thus slowing your tempo. I intentionally withheld cards such as Bower Passage and Reconnaissance on the basis that even if you find yourself stuck with many weak fliers with no form of precombat control, it is unlikely that in at this point in a multiplayer game, all opponents will have scary fliers. In short: if you don't own the sky with this deck, you aren't doing it right.
Final note: this deck is budgeted. There are a few better cards for some slots, particularly lands. I have intentionally avoided them to make the deck more affordable, and I do not believe their absence detracts greatly from the deck's effectiveness.