I was thinking that too. That whole scene, really. "They came up with a series of equations that tell us where the island will be at a given time". Oh really? That's it? Just some random equations? No explanation about what they are, how they came up with them, etc.
If it's true that this episode and next week's were considered "interchangeable" and Carlton Cuse decided he wanted '316' to air first, I think it was a mistake. Given all the unexplained shit that happened here, it would make sense that first we see how Locke got off the island, and then we see how the rest got back. Of course, if it ends up that he isn't really dead, then maybe it does make more sense this way.