I set my mom (62) up an old laptop running Ubuntu last year when her laptop was stolen out of my sister's car. She's adjusted fairly well to it. She needed a lot of hands on support at first and any time she uses her printer, but she has figured out how to do a lot of things on it on her own.
She makes papercraft activities in inkscape for a weekly storytime she hosts at a bookstore and has gotten very proficient, but still needs some hand holding when printing errors crop up.