It's little like beeing an administrator on the Windows system. It gives you privilegies to anything on the system. It is a big security treath to become administrator but still most windows user put them selves as this. On the linux system you normaly start as a normal user and become a super user (root) only when necessary.

For a normal user of the maemo system the root is not necessary. You can install and play with the normal things anyway. But if you would like to become a power user you need it. Like editing config-files, overclocking e.t.c... and it is here the real power of the n900 lays. The abillity to tweak the hell of it.

I have been using linux for quite some time now but did use windows before. And i would say that the linux way is more logical though it can be confusing in the beginning.