Other than increased speed and capacity, Hard Drive's have undergone few changes in their evolution over the years. This could be changing though. Today BTXFormFactor.com covers the technology behind perpendicular Hard Drive's, and delves into other future storage technology such holographic storage techniques.
"The advantage is clearly one of capacity: when longitudinal magnetic particles are packed together, they take up much more space than if they were to stand upright, if they stood perpendicular to the platter. More than merely a matter of initial capacity gain, perpendicular recording technology avoids a problem which has been well known in the field for many years: the super-paramagnetic effect (SPE), which affects magnetically charged particles of such small size as that used in Hard Disk Drives."