Mint is based on Ubuntu, so going back and forth isn't a problem. Mint even uses the Ubuntu repositories, and you could always add the Mint repositories to Ubuntu. Beyond the initial desktop, Mint offers a few customizations (menus, themes, display manager, and probably a few others I've overlooked), but the directory structure and drivers are identical. I've got both Ubuntu and Mint (and Fedora) installed on my desktop PC. Both Fedora and Ubuntu run LXDE desktops; they look and feel very, very similar to one another, but have some obvious differences under the hood. I don't like Gnome-Shell, and I don't like Unity; I installed Mint because I wanted to experience the Cinnamon desktop. I have to say, it's been a pleasant experience.