For developers who are currently getting their feet wet on 1204 alpha you can now (soon) create Media Directors with a Raspberry Pi Model B 512MB. There are quirks and there is a lot that doesn't work. Enough functionality exists for me to call this an 'alpha' version.
So that people do not have to sort through endless forum posts to figure things out I will use the wiki for most relevant information.
MD creation instructions are available in the wiki - http://wiki.linuxmce.org/index.php/RaspberryPi
Development status can be checked/followed on the Porting Raspbian wiki page - http://wiki.linuxmce.org/index.php/Porting_Raspbian
Bug reports should be made by filing trac tickets against the component "Raspbian/RPi MD" at http://svn.linuxmce.org/
I'll do my best to answer questions and help people out. Find me on irc.
(and thanks to posde, tschak, golgo, l3, hari, merk, and everyone else for continuing to encourage me!)