Finally got to go walk around, and I have to say, 343i actually blew this one out of the water. I was frustrated at first by the lack of hills, but hot damn, does that seem like a minor complaint now. There are almost no kill zones on the map besides under the water and one that is so far away reaching is it actually difficult. The new trees are awesome, especially setting them to normal and making them look fallen over. The rocks, too, are perfect: big and flat for the most part plus a few very natural looking ones.
You can even get inside the islands and build in a cave/ grotto like setting. My perspective on these has shifted a lot. 343i was paying attention.