I disagree, the challenge in a map was never constructing it (after ghost merging), it was designing it. That challenge is going to be ever present and I hope to see more guides on map design theory and less on how to put blocks into each other.
I will miss the battle rifle. Not because of it's power or how much you could own with it, but because it was the only burst fire weapon in the game. Now we have THREE 1X zoom single shot weapons. I mean, they should have made the needle rifle burst fire, because it seems like when I pick up a DMR and then switch to the needle rifle and then switch to the pistol, I'm just shooting the same gun. Sometimes I wanna switch it up. But I'm sure I'll adjust and soon forget about the battle rifle, much like I forgot about the halo 2 battle rifle when the halo 3 one came out and I disliked it. I will also miss duel wielding. I liked the fact that you could combine weapons for a more powerful weapon if you were willing to sacrifice the ability to throw grenades. Sometimes I'd pick up a weapon literally during a battle and shoot for a little bit to get the upper hand, and then drop it and finish the guy off. It made things interesting. It seems like going a step backwards to take it out. I saw it as a feature.
RIP chopper I think Bungie realized it was insanely overpowering in the hands of the greatest drivers, yet difficult to maneuver and only good for a few kills in the hands of an inexperienced driver. Splattering banshees was incredible.