Has anyone else had trouble with the online co-op? I've tried to play it with 2 different people, and every time the 2nd player always suffers from a slight lag. Wanted to see if anyone else out there noticed this or if it's just me and my "amazing" internet speeds.

Yeah, unfortinatly that is a huge weak point of every Halo game.

I've read if host turns graphics to original it works better. Give it a shot I guess. I played the first three lvls w/a friend and it worked pretty good for us, but this has been an issue for sure.