If you use any UNIX-type system, even Mac OS X, you want to be a normal user most of the time. That way, you don't have to tiptoe around wondering if you might damage something. I don't know what the score is on the Mac, but on Linux, for those times when you need more, you have the "sudo" command, or "gksudo" for running graphical applications as root. Or, you can go "old school" and change the root password to give you full control over the root account - just be careful, it's a loaded gun. (My current netbook installation is the first time I haven't done that, actually.)
As for problems installing Ubuntu "Feisty"... that was 4 versions, or two years ago. It's gotten a lot better, and the standard disc works as a "Live CD" too. If you fancy trying it again, I suggest waiting till mid April, when v.04 "Jaunty" should be on the cover disks of the Linux magazines on the shelves - unless you don't mind downloading huge ISO files and burning discs, that is.