Like Microsoft said, they would update the list whenever they can.
With this update, it added about 6 games, all Tom Clancy. These were VERY popular games, and it is a pleasure to see all of these added.
Edit: Forgot to mention. To receive the update via Xbox Live, place an older Xbox game in the Xbox360 and you should be prompted that there is an AU to download. Download that and you should be set. If you have any problems head to the Xbox.com forums. (forums.xbox.com)