Native Blu-ray support - Windows has partnered with PowerDVD to offer support in W7. No word if it will be a clumsy plugin like Vista Media Center or true integrated support.
So it would appear that by partnering with PowerDVD (however they implement this partnership) that support for HD DVD probably won't be available in Media Center. Back to the desktop and ArcSoft TMT.
Nice first look though, thanks for the writeup.