I thought there was an issue with the HD-DVD drive reading slower than the DVD drives, hence making a 2-in-1 drive not feasible as the 360's game disc (dvd) need to be read at a certain speed to run satisfactorily on the console. the hd-dvd drive doesn't reach those speeds. i guess these technical limitations can be overcome by the wonderful engineers at their disposal. then again, i'm no techie ...