I have given a copy of ubuntu to many computer illiterates who are still happy users, so it can't be too hard. And there's lot's of help and support from other users, for the FAQs and the not-so-FAQs, too.
From my professional view I find the concepts used in some of the user interfaces extremy smart and (at least mostly) intuitive. You can just give it a risk-free go, too. Download the current ubuntu CD, toast it and let Your PC run from that CD, it will start a full-fledged ubuntu linux without touching the PCs harddrive, so when You remove the CD, it will never remember what happened.
