Galileo seems to be what they are calling the environment the USB boots to. This environment is moving from the XFCE desktop environment to the different KDE plasma desktop environment. These environments can both be customized, but they are very different under the hood. I imagine that you can still choose XFCE and other desktop environments from the installer.
Before Chromebooks, my towns school system had netbooks which were pitifully slow on Windows. They installed Ubuntu instead. The netbooks still sucked, but probably sucked a lot less.