As far as ejecting the disc, here's the behavior. I assume you all know that the tray ("play the game") icon in the dashboard is now split into two? The top is for a game in the Xbox and the bottom is for the HD-DVD drive. If there is a HD Disk in the addon, the only option you will get is to play the movie. if not, you get the option to open the tray. The media remote "open/close" only opens the console tray.
One other thing, I wish there were a way from the dashboard to turn on/off the addon drive. I'm sure it's not taking too much power in idle, but I'd just as soon have it off if i'm not using it. I could unplug it, but, yech.