"Not to be a dick, you should totally install Ubuntu on that computer instead of Windows." Ya that'll play over well especially since you underestimate brand identity. Alot of people will refuse to move over to Ubuntu from either well known markets of OSX / "Apple" or Windows.
Because it's great and all for users like us should we choose to do it, it certainly won't play over well for those people since in the end, command line will eventually be needed for maintenance at times. What happened if there was an issue and they need it resolved so they took it to a local shop or Best Buy's Geek Squad. They'll probably be clueless and suggest that they need to "upgrade" to Windows even though it's not necessary. So it ends up costing more money, more problems, more headaches etc. I was an IT consultant for my brother's business which the businesses and government organizations I worked with are incredibly sensitive to change. It's certainly no different from residential users.
Sorry, your idea isn't that well thought out.
Actually, I did this with my mom and sister due to me getting tired of nuking her windows XP intstall (sis would download everything... good, bad, worse) and as an experiment. Mom was fine with it till she went back to college and they required Office due to the books.
Never had to touch a command line.
As with any experience, some people are successful with an endeavor, some people fall flat on their face. Everyone is now running windows 7, except the sis who's account auto-starts an XP VM.