I run web and file servers for my girl's office on a headless Ubuntu server (ssh and sftp only). At home I run Ubuntu desktop on her machine and mine, although I do use other distros (not too excited about the zeitgeist part of Ubuntu although I do like Unity for now). The Ubuntu system is solid. Actually, the only reason she boots Windows is because some websites she uses for business require IE. We haven't tried IE on wine yet. So I don't know if she could use it that way.
But, Ubuntu has some downsides. Zeitgeist for one (wth?). And the desktop, although easy to use at present, is rapidly turning into a "tablet for 3 year olds" kind of thing. Depending on which desktop you choose, it could be quite bloated. In Ubuntu's defense though, you DO have a choice of desktops. So..Ubuntu is still my distro of choice. However, Debian is my fallback distro. Been looking at Fedora as well.