I got it and played through the first 2 or 3 missions. its Halo 1 plain and simple it just looks and sounds much better, the remastered sfx are pretty amazing actually, it plays nearly exactly the same, you are forced to use the reach layout for the controller but thats the only real difference, They also added in dialog and some additional cut scenes with more story elements in some places improves the flow
i set it on heroic and it seemed easier then i remember but that could just be because im so familiar with it and all that, im gonna reset it to legendary see how it goes