Gabe and Tycho seem to have the same opinion of Halo 2 as Halo 1: they love multiplayer and hate the campaign:

I havent talked about Halo 2 yet but thats because Ive been playing it every night. For me its a lot like Halo 1 in that I lost interest in the single player campaign almost immediately but Ill be addicted to the multiplayer for months. Tycho beat the entire game and he assures me that Im not missing anything. In fact when I asked him about the ending he swore and kicked over a chair. I dont really care about that though as what I was looking for out of Halo 2 was an improved multiplayer experience. The addition of Live play along with new weapons, levels, modes, abilities and the possibility of DLC is enough to make me happy with my purchase.

They are playing online as the Halo 2 clan Team Inferno.