Well, after using this board in a server, I decided to buy another one to use in a small home theater PC. That was a huge mistake. The graphics performance is abysmal with absolutely no support from Intel (32-bit drivers suffer, no 64-bit drivers, and no Windows 8 drivers; all Metro apps crash). I really like this board otherwise, given how low power it is, but this is not suitable even for basic 1080p playback. Does anyone have any suggestions for a similarly low power board that has decent integrated graphics (that at least supports 64-bit and Windows 8 )?

P.S. You can read all about the lack of Windows 8 support on the Intel communities web site http://communities.intel.com/thread/29583. It's unacceptable that a new motherboard does not support an OS that was released in the same relative time frame.

Yeah, the driver situation for this generation of board is quite a shame! A black mark on Intel's record really. First the delays in making the hardware available and now they seem to have given up on proper support. The next generation is going to have proper Intel GPUs. I don't know why someone didn't call this disaster off when it became clear PowerVR was going to be a problem. I have to say I didn't see this mess coming because I trusted Intel.
That said, I recall getting 1080p playback to work when I was trying out the board. I've been using mine as a headless server so I haven't been using the graphics since my initial tests.

The problem with suggesting alternative boards is that you don't state your requirements.
1080p playback has different requirements depending on the codec (and also on the interface I guess). Some 1080p files won't play properly on (most) dedicated devices or even on computers that are a few years old.

If you're OK with something which isn't fanless (stock anyway), you could get a DC-powered Sandy/Ivy bridge board with a cheap dual-core (well, not cheap relative to Atoms obviously). That should playback virtually everything. It wouldn't be quite as low-power as the DN2800MT but it shouldn't consume much more at idle and you can underclock to keep peak power consumption reasonable.
There are of course Atom boards with better integrated graphics support and/or discrete graphics but I suspect they wouldn't be satisfactory for your purpose. And the next generation isn't going to be available any time soon.
Then there are the low-power AMD boards like the Zacates. They consume more power and (so far as I know) there are no DC-powered versions but the GPU is decent. I don't know about the Windows 8 support and what exactly they can play back though. And maybe there's new AMD hardware in the pipeline?

If you want low power, decent graphics drivers and cheap take a look at the Celeron 847 based boards that have come out recently. Same price range as Atom boards, but the CPU is just a slow Sandy Bridge with Intel HD graphics. Uses the same drivers as any other Intel HD chip which work fine in Win 8 x64 and supports 1080p playback. Downsides are a bit higher power consumption and possibly needing to work on the cooling to make it quiet enough.

Here is a thread about the Asus version, but there are others:
http://www.silentpcreview.com/forums/viewtopic.php?f=28&t=65656

I decided to go with the Intel DH77DF mini-ITX board. It supports LGA 1155 CPUs, so I may through in a low TDP i3 or i5 that has the Intel HD 4000 GPU. Thanks for the suggestions.