Partitioning can speed up your operations if you establish the first partition as being the area you install your operating system and all applications on. You would then keep all data, media, and documents on other partitions. The logic behind this is that the first partition is closest to the spindle of the drive and less spin time will be neccesary to access the data there, thus giving you faster read times and operation. I haven't been able to do this with my OS x but I have with an external that has my ps and fcp scratch disk... The result was pretty fantastic.
Let us know if you do it with you operating sys, and the results. My next clean install will be done this way.
Nf