Your whole squad gets a turn at once, and you can switch between characters at will, and give them commands until you use up each characters action points, or end your turn. The engine has been built completely from scratch, both graphics and code. We've extracted what data we can from the original tables, but otherwise it's a clean slate. We also have vehicles. We have combined all that Fallout stuff with the new squad based combat system to give a new dimension to the game.
Lets talk about the games atmosphere.
Interplay is providing us with the ambient sounds and music, which from what I've heard so far are going to be great. The graphics of the game do a great job of representing a war-torn world that's been reduced to wasteland. All of the dialogue, which the player gets from talking to the NPCs, is recorded by character actors so that helps as well. Also just about all the NPC have floating text. All the allocation of resources and travelling from one mission to the next is done in every natural unobtrusive way.