Well, I played a lot of online Quake(the original TF rocked fucking ass) and kept up with the community pretty good and I never saw any sort of functionality like the replay system that Halo 3 has. I could be wrong, but I never saw or heard of it.
Bungie knows that multi-player is what makes Halo. I, for one, am glad they spent more time on online play because I knew that would be where the majority of my time with the game was spent. I played the campaign co-op a couple times, it was alright, nothing special, and then I went onto the meat of the game.