For testing I moved my NUC into the den and have been giving it a workout. For those not following along it's an Intel Celeron with 4GB RAM and I'm using a 8GB USB flash drive with OpenELEC... no hard drive (at all). Cost wise it's a 4GB Xbox 360S (not on sale). I'm using its dual HDMI outputs... one goes to the display the second the AV receiver.
HD playback works like a champ and using SAMBA via my NAS I avoid using DLNA and its many limitations such as the lack of title indexing. Only thing I had to configure was adding a couple of video driver resolutions to get perfect playback (59.94 and true 24). Here's a copy of the file you need to drop into the /storage/.config/xbmc folder (xorg.conf)...
VendorName "INTEL Corporation"
Modes "firstname.lastname@example.org" "1920x1080@24p" "1920x1080@60p"
HorizSync 14.0 - 70.0
VertRefresh 24.0 - 62.0
Option "DPMS" "true"
Modeline "1920x1080@24p" 74.230 1920 2560 2604 2752 1080 1084 1089 1125 +hsync +vsync
Modeline "1920x1080@50p" 148.500 1920 2448 2492 2640 1080 1084 1089 1125 +hsync +vsync
Modeline "email@example.com" 148.352 1920 1960 2016 2200 1080 1082 1088 1125 +hsync +vsync
Modeline "1920x1080@60p" 148.500 1920 2008 2056 2200 1080 1084 1089 1125 +hsync +vsync
# fixes tearing
Option "Composite" "Disable"
Germaine to this thread I have been testing ServerWMC and its client. So far I'm very impressed. I'm using Windows 8.1 Pro Preview as a WMC backend and all playback has been via OpenELEC/XBMC NUC. Now I'm OTA only so obviously my comments relate to such.
The experience is different than a WMC extender but in most cases very similar. You can view the guide, schedule and play recordings, watch live TV, etc. So far my only complaints are... channel changing is slow but since I hardly ever do it I don't really care. I haven't (yet) found a way to display recordings in folders (for series). The one I do care about is viewing a recording while it's still being recorded. Basically, you lose trick play features such as skipping commercials (of which you can do once the recording has finished). I watch a lot of commercial delayed shows so this a biggie for me. I'm guessing if you have a spare tuner you could simply watch it live (not the live recording) and have the trick play stuff available... I'll have to try that out.
Again, the experience is very different and some things I like better than WMC. The interface is a little slicker and the harmony remote is very easy to customize. Here I changed the default skip forward and back times (advancedsettings.xml)...
My initial impression is I would never buy another Xbox (as an extender) unless it was under $100 or needed to be 100% idiot proof. OpenELEC takes about five minutes to install and the ServerWMC and client another five minutes. So after 30 to 60 minutes you are good to go. If you are like me and you enjoy casual tweaking it's also a wonderful outlet. Not complex at all nor required but you can tread as lightly or as heavily as you wish. Your entire installation resides on a flash drive and OpenELEC has a built-in backup/restore that will let you return home at any point in time. You can even give it a test drive without messing up your existing PC. Just configure it to boot off of a USB flash drive and install away - just be sure not to select you hard drive during installation!