Hopefully they intentionally buried their weakest announcement in the middle. We'll know in 10 minutes. Alas, I bet the third announcement is just their custom controller they've mentioned in the past.
I was expecting the SteamBox to be announced with the controller details, and something really cool to be the third announcement.
I also hope the eventual SteamBoxs are as compact as the Nintendo Wii is. While not the most powerful thing in the world, the Wii was really compact and straightforward in design (when laid on it's side, instead of standing up on the stand).