I recently installed PC-BSD on a computer for a webserver. Despite it being my first BSD installation, I was impressed. Once it's setup it's suprisingly easy to use and there seem to be plenty of applications out there. The PBIs are great, but there could be more.
My father is computer illiterate, but has a 4 year old computer that he uses for internet and e-mail. He wouldn't be installing any programs, and the few he'd need are available in PBIs. His computer is an old emachine that came with windows ME, after the third reload I "upgraded" him to 98SE.(it can't run 2000) I'm thinking that PC-BSD could give him a more reliable OS and similar or better performance then windows ME.
Also, my stepmom, who is better at computers, uses MAC OS at work, is there an easy way to make BSD look and feel like OSX? This may be the best option.