Support for the Xbox 360 has landed in master. You need:

• gupnp master0.13.3
• gunp-av master0.5.5
• gupnp-vala master0.6.5
• rygel master

For the transcoding to work properly make sure you have gst-lame and gst-ffmpeg installed.
On a side note: Rygel master has now gained the ability to serve subtitles to Samsung DLNA enabled TVs