While the new NVIDIA chipset will help with BluRay a bit, the 2.0 CPU may not have the power to do it flawlessly - I'd wait and see how it tests.
But dumping MCE? What are you planning to use on the MacOS side, which would do stuff like BluRay, AVCHD, or has plugins for stuff like netflix? Or it has extenders?
I use Macs for everything else, but for Home Theater Apple is a few years behind. I replaced my Mac Mini (running Vista Media Center) with an AOPEN and haven't looked back: http://usa.aopen.com/products_detail.aspx?ctgr=74&Auno=2878&mdstl=309
I really use my MCE primarily as a DVR only. For BlueRay I have a PS3 and my AVCHD work is done on other macs. All of my content is served up to my TV's by either the PS3, a PC itself or an Xbox 360 running extender software between the Macs and those platforms. I will look at the aopen page though.