Ryan pointed me to this post by Scott Hanselman.
Now, I'm not sure I really need an RSS feed of the Halo 2 games that I played (though I see why you'd want it for a clan), but I'm pretty impressed by the game viewer stuff.
I looked at a rockets game on Ivory Tower that I won last night, and with Game Viewer, I can see all the places where shots were taken from, and where people were when they died. I'm not sure what I'd do with that information, but it's really cool.
Oh, and I found that Bungie did include Blood Gulch in Halo 2. The terrain seems identical to me, but there are some additional rocks for cover (a good thing) and the bases have another level in them. The level is named: