Just thought I post what works as I read this thread before I bought:
OS: Windows 7 Ultimate 32bit (x86) RTM (Final Build)
TV: Samsung 40" LNA530
Installed the OS on the ASRock with only minor interactions. It was pretty easy. It detected the Samsung TV and picked email@example.comHz. Then went to Nvidia.com and got the chipset, graphics, and audio drivers for Windows 7 32-bit and everything worked. I mean everything. Networking and copying files from my macbook was perfect. 32 MB/s or 250 Mbps since both have gigabit ethernet and so is my router (D-LINK DIR-655). I have an average case for my USB HD and that reached read/write speeds of 30MB/s as well...didn't really think about getting eSATA, I mean, that's fast enough!
Also, I tested the following:
1. 1080p Simpson mp4 trailer. Perfect, and low CPU
2. 1080p mkv (encoded in H.264) movie. I installed http://labs.divx.com/mkvwin7preview
for Media player to recognize it and this http://sourceforge.net/projects/ac3filter/files/
for the Audio to work and it was perfect and low CPU. The MKV codec is a tech preview but works good enough for me. With it, the decoding is offloaded to the GPU, rather than the CPU.
3. 1080i m2t (which is AVCHD I think - the interlaced video of a Volleyball match from the Olympics off my PVR SA-8300HD). Perfect, and low CPU, and it even deinterlaced the Video!
This little guy can play anything. The 3 drivers, and 2 codecs (mkv from divx and ac3 filter) were the only things I installed after installing Windows 7. I used windows media player for all the video tests. Haven't tested the DVD player, but I'm sure it'll be fine. Currently adding my music library to Windows Media Centre and lots of my DivX movie rips.
With regards to the Audio, they do advertise 5.1 and such, but I only have a Stereo amplifier with 2 speakers. Don't hate. I live a 1 bedroom and don't have room
So I can't personally confirm much there.
Hope that helps anyone wondering if certain video files will work or not.