The cluster size in NTFS in today's harddrives really will not have any kind of real world benefits whatsoever. The cluster size by default is 4kb. If the system was running a harddrive on fat32 and smaller harddrives, the cluster size would be smaller by default,.. and more overhead per cluster when transmitting that data when called for.
If you are running win95, win98 or winME and using a smaller harddrive,... 2GB range, then you would see a performance increase with larger clusters than say 512 bytes which was common. If you move that to 4KB you would see higher data transfer rates in "burst mode" but would waste more space, which was very very important consideration back in win98 era with say a 4-16GB drive.
In today's world, on NTFS, huge harddrives (at least in comparison to then, maybe not tomorrow), quicker interfaces (instead of ide66, eide100, eide133, now sata I and II typical), there really won't be any real world benefit to cluster size. I should say it is a benefit as long as you don't decrease it.
In other words,... no reason to mess with it. Partitioning used to have some possible performance increases as well in certain situations,... not really true with today's hardware as well. Some of these things applied when hardware was fairly slow in comparison,...