Seagate already has the number one spot for desktop hard drive capacity, so the natural next step for them is to make their existing drives better. They've done that with an increase in density, announcing the first volume shipments for 3.5" drives utilizing 500GB size platters, resulting in a density of 329 Gigabits per square inch. This is first realized in the Barracuda 7200.12, which aside from the density is just like any other Barracuda drive.
Higher density leads to higher performance, requiring less effort for the drive to read large amounts of data. It also can ultimately result in lower drive prices, since less physical material is needed. And, perhaps most important, it leads to higher capacity drives. With platters of this density, 2TB hard drives could be just over the horizon. Or, perhaps just as cool, 1TB laptop hard drives.