While this isn’t a MythTV build, I have not had a MythTV computer for 2 years now. Instead I have been using a Apple TV 2 jailbroken with XBMC and Firecore installed.
I love XBMC but it’s pretty buggy on such slow hardware and because all I really do is stream movies from my NAS and watch netflix, Firecore has a much higher WAF because everything is in one interface.