... fed up with watching programmes downloaded from the BBC iPlayer on my PC I decided to try one of these "Windows Media Externders" and play them on my main TV. Picked this one based on price and have had it for about 6 weeks now, so can give a review of my impressions so far. The idea with these devices is that they can play video or music stored on a Windows computer remotely.
The DMA2100 can work using wireless or an ethernet connection. I've been using minbe on a 802.11n wireless network and it works fine for me despite the signal strength inidcator saying its maybe not good enough for TV.
Set-up was a bit of a chore for me because my PC is upstairs and the TV downstairs so I had to go up and down a few times, but once the PC & DMA2100 had hooked up its been fine. Then manual and on-screen guide shows all the steps required, it would just be easier if both devices were next to each other (which is unlikely and sort of defeats the purpose of a media extender ..). This comes with a remote control to add to your expanding collection too ...
I've used this to play things downloaded from BBC iPlayer in WMV format and its really good for that. No problems with the wireles signal for me. One annoyance is that it's slow to fast-forward or rewind a programme if you watch part of it, close it then come back.
I've also used it to view photos and music from the PC. These aren't why I bought it, but are nice extras. Viewing photos is fine - except when they are rotated. The interface for the music is nice with a visual album cover view that you can flick through. You can have music play with a slideshow of your pics which is also a nice bonus. I had hoped to be able to scrobble songs to last.fm through this as its using Windows Media Centre, but so far haven't been able to achieve this, but that's an aside.
There are some other features which I haven't used so am not in a position to comment on.
I'm not sure what the future of these types of devices is with Windows 7, so it may be worth checking on that if you are concerned about it stopping working some way down the line.
All in all I really like this and its good value at the current price. It lets us watch downloaded TV in ocomfort on our main living room TV rather than huddled round the PC perching on rickety chairs !