According to this piece:
With its budget price and improved multiplayer, there's more than enough here to cheer nay-sayers.
One of the most striking things about Warhead is the way it shakes the template Crysis snowglobe and has its constituent parts drift and settle into surprising new patterns. In Crysis encounters with enemies were heavily cordoned off from each other, in Warhead anything goes.
It's a frenzy of intelligent and original level design, far away from the Far Cry model that Crysis aped."
There's more through that CVG link. The game's out this Friday in Europe.