There isn't a limitation such as the one with MCE 2005. I'm joined to a
domain just fine and using my 360 as an extender. Here's the snip from my
other replay to Sandyman08 & Falchion in another thread.
"I had the same problem which was resolved by disabling the network firewall
feature thats built into windows... since my computer is on a private network
anyway, there isn't much point in running the firewall since its already
firewalled at the router level.
So far I've gotten all components to work just fine (Media Center and Media
Library Sharing) with the exception that the direct access from the 360 into
the media list (ie through the console not media center) doesn't list all of
my artists or albums, quite irritating. "