Given the download size, I think we are very early on in the realm of DVD ISOs. I've only seen one or two very special instances of a DVD ISO being made available for temporary download (KNOPPIX-DVD beta comes to mind). Maybe the boom in DVD burners this year will encourage the presence of larger ISOs.
The jigdo method (I wish other software houses would start using it!) is about the best thing since sliced bread.
-SUO