Mint makes a GREAT Myth base as the codecs and drivers are all preinstalled.
Just go to Synaptic and install Mythbuntu-desktop. Wait for a while and all the dependencies will install. If you're using a remote control, the lirc GUI will pop up during configuration and ask you for details. Most likely, the restart of the lirc daemon will fail. You can manually restart it with "/etc/init.d/lirc restart". Now, you should run the Myth Config utility, now available through MintMenu. Assign the proper backend server (the computer you're using or another if you're a hardcore geek like myself), add whatever plugins you want, and then run the frontend. You should now be golden.
You can login to the normal Mint Gnome desktop or the XFCE Myth desktop. I don't use XFCE, but Myth runs just fine...