I know it's another operating system that's simpler and customisable and free, however that's about it.
Simpler than what?
The guts of Linux are easier to maintain for a longtime geek with command line skills than any bit of RedmondOS. Also quite a bit more satisfying (fixed stuff tends to
stay fixed, as opposed to randomly breaking again for no good reason).
So, it looks like I want to use debian as my distribution, because I'm going to be wanting to use it on a mac box.
As long as it is a fairly recent Mac (imac or newer). And, BTW, once you get past the partitioning, Debian on a Mac is
exactly the same as Debian on a PeeCee.
As far as partitioning, probably the Debian installer will handle it for you OK. I always do that part manually, because I have my way I want things to go, but there are automatic options.
Ubuntu's security model is like OSX's (no root user, run admin stuff with sudo).