A lot of us are wondering why Ben had to break through the Orchid's fancy chamber vault, and use the ancient looking wheel instead, to complete his task of moving the island. Some comments of Ellen's on the TLC blog led me to a few thoughts about that: "...the fact that Ben had to blow a hole to gain entrance and then chip huge icicles off the wheel with a tire iron leads me to think that it hadn't been used since the Dharma Initiative arrived and built the Orchid Station." What she said made me think that maybe it's like the difference between the results of an atomic bomb blast, and an atomic power plant.
The FDW itself seems to be a crude but powerful apparatus that might be difficult to control for applied purposes beyond it's original intention, whatever that may be. It would make sense that the DI would have had to refine and upgrade the mechanics of the ancient machine before they could utilize it. With modern equipment to regulate the power, they could create a more manageable process, so that it could be used in various controlled and specific applications via the vault and instruments built onto it. Maybe the DI had even tried out the FDW for themselves when they found it, created an incredible result (moving in time or space), and then built equipment around it to harness the energy for practical purposes. So instead of trying to get a handle on an atomic bomb, they built a modern system onto it and learned to use it as a moderated power plant to run their futuristic equipment. Like Ben said, it was used for experiments with bunnies, so it seems as if the DI did not get very far along in their tests with wormholes, or whatever, before they got purged out.
Then when it came time for Ben to move and hide the island, the refined vault apparatus itself was probably of no use to him in doing what he had to do. He had to quickly get to the true power source, i.e. the big guns that were covered up, and turn the FDW to get the huge blast that he needed. And voila, the island "moved". Well, it's just a thought.