Picked up a BDV the other day...
Sounds decent, love the wireless rears, decently priced HTIB.
I have a Samsung plasma, xbox 360, and a Motorola DVR DCX3400. I'm thinking it's pretty much impossible to get Dolby Digital out of the Xbox/360 in this setup, unfortunately.
In order to get DD out of the cable box, I have to use a digital coax (who came up with that name for a glorified RCA cable, lol).
Regarding DLNA
What a PITA this is. Soooo picky. Anyhow, this is what I've found.
Microsoft Windows 7 DLNA is pretty crappy. Works ok with the Xbox, does not with my samsung TV nor the BDV. All devices see it, but only the Xbox/360 will actually play any of the media.
Before I got the BDV I successfully streamed media to my Samsung TV using
http://www.serviio.org/ Once I got the BDV, I wanted to use that as my streaming server (figured the DD would work better, plus the interface is a little nicer).
None of the profiles that came with servvio seemed to work with the Sony, so I created a profile using some help from the support forum
http://forum.serviio.org/viewtopic.php?f=5&t=664#p3682
and it works! I haven't thrown everything at it yet, but it seems to play avi, mp4, divx, and h.264 so far.
It's unfortunate the DLNA is so darned picky, I can't create a single media server that 'just works'. Once I select the profile for the Sony, the TV's DLNA doesn't work anymore but I'm happy enough with it working for the Sony.