I've been doing some more testing of Toast 9's HD DVD creation and have run into a few more issues:
1) I mentioned before that H.264 encoding doesn't work. This continues to be the case.
2) Even with MPEG2 sources, Toast 9 sometimes crashes when making an HD DVD, albeit infrequently. The good news is that Toast 9.0 is more stable than Toast 8.0 was.
3) With MPEG2 sources, even if Toast 9 finishes the burn process, the disc may lock up in certain parts of the video. This is not a media problem, because even if I save the image to the hard disk, playback will lock up in the exact same spot. If I do burn the image to disc, playback will stop in the same spot on both my Toshiba standalone as well as in DVD Player.app on my iMac. However, if I start over and make a different encode with same source material, the resultant HD DVD may work fine.
4) My Xbox 360 HD DVD does not like these discs. The disc will load and go to the menu, but I cannot navigate out of the menu to play the content. I tried using both my Logitech Harmony Xbox 360 remote as well as the Xbox 360 controller.
I have not tested Blu-ray because I do not have any Blu-ray playback device at my disposal, and DVD Player.app does not work with Blu-ray. I will likely buy a Blu-ray player once there is a Profile 1.1/2.0 player below about $200-250, but I fear that may not be until 2009.