Hi M_R,
From my experimentation the whole UPnP/DLNA area is still half baked in many areas (and not just in MC13), but industry wide with no clear market leader from what I can see though development is going well. For a sucessful UPnP/DLNA system I've found you need two things:
1) Meta Data Presentation Layer: How is the Media Receiver going to browse the servers Library. While many just use a file structure, MC13 would have a clear advantage here
2) Streaming: Most will do this fine, pick a item and it (if it is compatible with the receiver) it will play
3) Transcoding: The holy grail is for the Server and Receiver to negotiate what formats should be used to stream the media (Audio/Video/Pics) and then have the server perform on the fly transcoding to suite. Eg - I have my music all in WMA Lossless which the PS/3 can not play, so the Server needs to transcode this on this fly --> MC13 will use MP3 and
www.tversity.com will let you choose many formats including PCM! , and This gets the most interesting as this is where I think MC13 could shine given it's flexibility to build custom filter graphs etc. The same concept needs to apply for Video formats as well.
I've had a play using the PS3 but as my interest was more in streaming/tanscoding Video than Audio/Pics, MC13 is a poor candidate at present. You should be able to get MC --> PS/3 going for Audio (if your happy with transcoding to MP3) / Pics just fine, but you may have to play around with some of the settings in MC13. If your after something that will stream/transcode Video / Audio (incl PCM) / Pics using UPnP/DLNA then the best results I've got so far (and there are still issues) is to use
www.tversity.com for UPnP/DLNA streamng/transcoding but of course you don't get any of the MC data presentation, just a file structure.
Good Luck and I'm intereted to hear how you go....
Nathan