So far, the biggest problem getting people from using Windows to using #Linux is that there are a million different distros and 500+ solutions to every problem you can encounter. It's overwhelming. It then becomes an "evil I know vs the one I don't." But what the hardest obstacle for me is explaining that EVERY combination of distro versus solution is about 80% valid as long as you are willing to use your head, where as Microsoft would rather you use your wallet and be too scared to leave.