Andrew wrote this a while back on this thread http://forum.linuxmce.org/index.php?topic=7904.0
"Yes we have several on test now....and with updated drivers they work great I am pleased to announce.
We have updated the nVidia & alsa packages;
- nvidia-glx_1.0.9639 (ie 180.51)
We have also updated/extended the avWizard to allow you to choose more output connectors (ie HDMI-2 as in the revo) and also to allow you choose to route the audio (PCM, 5.1 surround, DTS) over the HDMI connector if you wish to. These updated packages will all be in the 0810 trunk in the svn shortly...I hope next week...so will then be available in subsequent builds.
So far the Revo has performed really nicely. It has some minor limitations such as no S/PDIF out but now we have enabled HDMI Audio this really is not an issue. It has very simple and easy to fit VESA mounting bracket so that it can be mounted either directly onto the back of your TV screen or onto the wall behind your TV. The physical shape of Revo is well thought through for when its rear mounted - the power on/off button points upwards, making it easy to get to and all the USB/HDMI/VGA/eSata/Memory Card connectors are easily reached too (this is much better than on the Eee Box as they are more spaced out). The Revo has a very quiet fan that is barely audible even in a quiet bedroom (in non scientific tests I would say its as quiet as the ASUS Eee Box). We are testing the 2gb RAM/160gb model but there is also a 1gb RAM/8gb SSD model that comes with Ubuntu on the SSD and no Vista license...this looks to be the perfect model for LinuxMCE (you might need to add more RAM for 1080P though).
The above driver changes should also benefit other nVidia based motherboards & graphics cards (we have tested the HDMI audio on an ASUS P5N7A-VM http://wiki.linuxmce.com/index.php/ASUS_P5N7A-VM