[dublinben]

>but doesn't have any options for streaming content over a LAN

This is simply not true. Plex has been available on the Roku for years. It's one of the most popular channels.

[Osiris]

Plex is terrible. It requires transcoding audio and video on the fly, which requires a hefty media server. XBMC decodes everything on the fly on the local box requiring no transcoding.