Summary: I'm using the DSM-520 in conjunction with the freeware TVersity software. I'm also using a wired network rather than rely on wireless. I haven't had any issues playing a wide variety of video and music files with this setup. The images are crisp, and the media plays instantaneously. I recently added Cidero to the mix (this freeware allows you to pick media from the server and control the DSM-520 using a computer).

All in all, the DSM-520 is an excellent piece of equipment for the money. I would recommend it to computer savvy users as well as an entry level users that haven't tried products like this before.

Summary: Allows you to share your MP3s, movies and pictures from your computer to your entertainment center.
Once properly setup (and it's not easy to do through remote and virtual keyboard on the screen), it mostly works. I am able to view standard definition movies over a 801.2g (54Mbps) wireless link from a DLink DNS-323 network-attached storage using uPnP. The movies play smoothly. Most movie formats are not supported though, but standard MPEG2 is.
Unfortunately, some remote features are really lousy, for example the fast-forward only speeds up by about 25%...
Also beware, this is the 2nd unit I used. I had to return the 1st one because it froze while upgrading the firmware - a deadly condition according to tech support.
Other features include online radios (most for a fee) and online TV. Unfortunately, again, the online TV viewing requires your computer to be on... which is not what DLink suggest in its advertising.

Summary: It can only play paid internet content live like Rhapsody, what about a few free internet radio stations that are already out there. That would really make this much more awesome. Nevertheless if you have AVI or MPEG (and other) format video files this is a simple way to get them onto your tv and with a remote control. Now if only someone would build some thing like this with internal bittorrent! Of course that would entail much more expense so this is great for now.