As I have been using the Extenders (see the the unboxing videos here) for a few days and I have had loads of questions so I thought I would try and put some of the points down here
5.1 Audio
I thought I would try a WMV file with 5.1 audio encoded in it. The file is a conversion of a DVD for which I used DVD-WMV. On my Xbox 360 when I played the WMV file it outputted the audio in 5.1 and my receiver decoded it with no problems. On the DMA2100 and DMA2200 the same file connected via digital audio cables it only outputted the audio in Stereo. I have a few films converted to WMV so this is a big disappointment. I did notice a setting in the Audio setup for the Extenders called "WMAPRO 5.1 decoding" with this set to Internal the WMV played the stereo track and with it set to External no sound came out at all while watching the file. My Denon AV receiver doesn't decode WMA pro so that is why there is no sound. This setting does not seem to effect any other audio. When playing a DVD the 5.1 audio worked fine (as did DTS)
Video playback
Video playback looks best on the DMA2200, for some reason it looks better than the 2100 but as I said in my first impressions post that could just be me. The main benefit with Xbox 360 is it will output 50hz as well as 60hz
Media Center UI
The Xbox 360 wins hands down on this, it's smoother and faster but the HDMI connection of the Linksys units does deliver a brighter picture than the VGA connection use on my 360. It would be nice to do this head to head with an Xbox 360 Elite using HDMI
DVD Player
DVD playback on the DMA2200 is good, put the disk in and it starts up almost straight away. There is an LCD display on the front that display the chapter details and the playback time. The picture quality is very nice, with all the settings left at the default it played back at 1080i. Pressing the "i" button on the remote brings up a information panel where you can select the audio channel, the camera angle etc. On the Xbox 360 I have got used to the DVD player and it works well for me but as with TV playback I think the HDMI delivers a more colourful picture and the Xbox is more subtle. I don't know whether its region locked yet I have no US region DVDs to try
The Extenders also have two major advantages over the 360, built in wireless and no fans. The units are silent even the spinning DVD is quite and the wireless so far has been working well. I am using a D-Link pre N wireless router and playback has been fine, even 720p content and the DVD WMV files.
DIVX playback should work on the Extenders, but I have not tested this as I have no files to test yet.
Both Extenders come with learning remotes (the head to head type)
So overall I think it depends on your situation as to which is best Extender for you. For me the Xbox works best as its a good extender and I am not bothered about the fan sounds, plus its an Xbox 360, but the Extender would work well in the kitchen or the bedroom where you want it quiet and neat and the DMA2100 is a small unit
I am going to carry on using the DMA2200 and see how I get on with it, if there is anything you would like me to test on it let me know