Miners will now only hit the node once to get all the ore and associated loot.
This change might seem mundane but it actually carries some significant weight. Farmers regularly fly or run around zones, stopping at every node they see. Under the current system most nodes required between two and four hits to extract all the ore, sometimes even more for the rich nodes. An ore farmer would spend a portion of his time ensuring the mobs were cleared around the node enough so that he would be able to hit it multiple times, and then actually spend the minute sitting on the node farming it.
With the one hit method that is now being implemented in 3.0.8, the process becomes significantly easier. Point, click, wait a second, fly off to the other destination, profit. There's no "???" in there, just a pure and easy way to make money.
For me this changes means that farming around zones such as Icecrown will become easier with all the elites that pat about. I won't really have to wait for the perfect time to land and grab the ore, now I just have to wait so that the elite will be out of range long enough to get one hit. Quite a nice little change.
One last note about this. We might see this change reduce the price of ore across all servers. It stands that if a product is easier to get, then supply will increase to meet demand, lowering the overall prices. While we'll have to wait and see how much of an impact this change has on the supply side, the results will definitely be interesting to look at when 3.0.8 goes live.