When replacing the OS, you don't need to worry about the home folder being
deleted.
Oh, and in my experience the home folder can be huge (owing to downloads,
etc), while the rest of / seems to only take 5-8 GB on my HDD.
Having a seperate /home enables, with many OS' installed on a HDD, a
centralised ~/Downloads directory for the ~/ folders in it (through the use
of links), minimising disk space usage (see above paragraph), or a
centralised ~/Music, ~/Pictures, ~/Videos, etc directory so no matter which
OS you boot to you get the same art, and changes to that only require
removing/adding once (rather than every copy of a piece of music in every ~/
folder). That is, assuming every OS on the HDD has users with different ~/'s,
all of which in the /home directory (partition).
