As you may know, Ubuntu 13.10 Saucy Salamander will ship with Mir by default and XMir replacing the old X.org. While Kubuntu 13.10 refuses to switch to Mir, in order to use Wayland, the Lubuntu team has also announced on their official site that they will keep the old X.org server , until Lubuntu 14.04 is released.
The Xubuntu developers(which have remained silent until now) have also decided to stick to X.org, until Mir will get official support for the graphics drivers. For now, only the open-source grapics drivers (from Intel, Nouveau and Radeon) work with XMir and Mir.
But the developers have released a testing version of Xubuntu 13.10 Saucy Salamander running on Mir, which can be downloaded from the official site.
Because it is just a testing release, the users are advised to use Xubuntu 13.10 Saucy Salamander inside a virtual machine, similar to VirtualBox or VMWare Workstations.