Regarding OS X not having software to play HD DVDs.. not (entirely) true. DVD Player does indeed play back HD DVDs... However, there aren't currently any drivers for the toshiba/microsoft drive on the system.
DVD player will playback VIDEO_TS and HVDVD_TS folders from the hard drive.. (Namely used for playing back DVDs created with DVD Studio Pro)... So, it looks like, at least on the OS X camp, we're just waiting on device drivers (and possibly support for physical drives in DVD Player; i don't know if that have that in already or not).