For facilitating more broad testing of XMir/Mir with an Xfce (v4.10) desktop over Canonical's Unity desktop, there's live XMir-based Xubuntu images available ahead of the Xubuntu 13.10 release. The Xubuntu team is presently deciding for version 13.10 whether to stick to shipping an X.Org Server by default or attempt to use Mir/XMir.
Those interested in trying out the experimental ISOs can find more details on xubuntu-devel. "It is of EXTREME importance that we do as many tests as possible as the technology evolves. We need to understand how our system will behave under XMir in order to make the decision later this month whether to move our standard ISO from X.Org to XMir."