I also played the beta and as the above poster stated, even over Live, lag is nearly non existent. In Halo 2, the host team had a distinct advantage over the other team and I bet if the numbers were available, the host team won 7-9 times out of 10. But all this is irrelevant as we are talking about Halo 3. I could never tell which team was host in the beta like I could in Halo 2, based solely on how much more damage the host team's weapons inflict. Every match in the beta felt so much more balanced than Halo 2. The beta was rad.
Do you guys realize there is a built in custom game editor? (Forge) It's budgeted, but players can spawn whatever weapons or objects they want into the game wherever they want, then save and upload the map for other people to download and play. I can't say that I have played a multiplayer console game that allows this, although I think one of the Farcry xbox iterations had a map editor.
The saved films look sweet too, you all can go back over your film and see exactly how I whooped your *** in that last match.
Believe the hype, as far as console games go, this is one of the few that's going to be worth the 60 bucks.