I understand why you decided to stop work on the Fan, but I have prepared a list of reasons why a Fan is not only worth the time required to implement it properly, but is also the most useful addition Minecraft could have. However, in order for it to have maximum functionality, it should push all entities, including falling sand, mobs, and players. Also, the distance entities travel should be determined by the strength of the redstone signal going in. For instance, a Repeater or Torch pointing directly at the Fan block would make the Fan blow entities fifteen blocks. Also, Fans would have to be able to face any of the six directions.
1) Enderman Farms: Currently, Enderman Farms are massive both in size and expense because Enderman teleport when in contact with water. Using Fans would greatly improve upon these farms.
2) Gold Farms: Without the option to place Water in the Nether, the only way to move the drops from where the Pigman die is to use Hoppers, which are ridiculously expensive. Therefore, the spawning platforms are never large enough to be very useful.
3) Wheat / Carrot / Potato Farms: Using fans to push drops instead of water means that drops from harvested crops can move to a central location without disturbing growing crops.
4) Mushroom Farms: Water will destroy all crops in its path, but Fans will only push harvested Mushrooms. This way, Mushrooms can remain to spread while their neighbors are being transported. This double the efficiency of an under-appreciated source of food.
5) Tree farms: Since Leaves take a long time to decay, Fans are the optimal method for transporting dropped Apples or Saplings. While the Leaves are still decaying, Saplings can continue to grow.
6) Sugarcane Farms: If Fans are able to blow through blocks that can be walked through (they should, in my opinion), then you can say goodbye to drops being lost and wasted as they get stuck in the block where the Sugarcane grows.
7) Melon / Pumpkin Farms: Again, if Fans can blow through the stem blocks, then Melon and Pumpkin drops will no longer get stuck in the stem block.
8) Redstone Wiring: Currently, neither Dropper chains nor water can transport items over things such as Redstone Dust, Torches, and Repeaters.
9) Item Elevators: With Fans, Item Elevators would no longer be massively expensive and sizeable contraptions requiring late game items such as Nether Quartz for every layer.
10) Player Elevators: Fans would be able to transport the player upward quite high when on full strength, then reset fall damage when the Fans are on their lowest power setting. With this combination, a very nice two-way elevator can be created.
11) Projectiles: When used in conjunction with Dispensers, TNT, Snowballs, Arrows, and Fire Charges can have their flight path modified heavily while they are in flight by blowing them with Fans along their path.
12) Minecarts: When a Minecart stops on an unpowered Powered Rail, then the Rail becomes Powered, you could use a Fan pointing in both possible directions so that you could choose which direction the Minecart would go. This would be very useful both for player Minecart stations and for Storage Minecarts.
I hope I have convinced you that Fans are worth adding and that they could be hugely helpful in fixing the issues present with current blocks and techniques. Fans are better than Hopper chains. So much better.