A PC in my media room isn't appealing at all. A networked appliance (I think they're being called "media hubs") that can go to a remote (in a closet someplace) media server and display/play content located on that server is very appealing.

I think most of those devices are based on Windows CE, but a few (the Apple for instance) are probably not. The Universal Plug and Play media sharing spec (created by Intel I think) seems to be the standard they mostly use. Server software is available for any platform one is likely to want.

I don't think a "media PC" in the form of a PC in the media room will ever catch on.

EDIT:

Although the world could use a good media hub gizmo from a non-computer company. I think Phillips actually has a reference hardware design available as well as a few products. Maybe Outlaw should think about a device based on an existing reference design like that? I'd buy a few if they were well thought out and nice looking.