See the other thread here where others (myself included) are unable to get the DLNA features under "Home Media" working:
http://www.satelliteguys.us/hopper-zone/280049-my-quest-get-dlna-working-hopper.html
The gist is, that this feature seems to have a lot of bugs that Dish plans on addressing with a future update. I was in a chat with tech support this morning that told me that the Home Media option does not work without a Dish Network Hopper Internet Controller. I don't know if I believe that or not. I think this is just a symptom of us being early adopters.
Once it does get straightened out, I would assume that this feature will function like any other DNLA streamer out there. As others have mentioned, PlayOn and TVersity are both good options. I use one called Serviio. I like Serviio the best because it offers a Windows Home Server dashboard add-in on my server, plus it can import movie data from XBMC NFO files. My entire 1100+ movie library is already scraped in an XBMC format, so this was critical to me. Serviio already works great with XBox 360, Sony Bravia HDTVs, and the Seagate FreeAgent Theater+. I see no reason to think that it wont work just as well with the Hopper/Joey.
But even after it gets straightened out, I highly doubt there will be an option to browse a local network and natively play stored media files of any format. This actually requires quite a bit more processing power to do. Transcoding through a DNLA server is a much more realistic option, so for those of you planning on getting this going, if you dont already use PlayOn, TVersity, Serviio, or some other DNLA equivalent, I suggest you get started on setting that up, so that you can have it ready for whenever time in the future Dish releases an update that gets this going!