The new AT-AT is smaller than its predecessors (except for one; 10178 Motorized Walking AT-AT has the same amount of pieces), but has a more robust appearance than previous versions. The head is a lot sturdier than before and now includes two spring loaded missiles underneath.
This is a description taken from LEGO.com. Do not modify it.
"... Who can stop the Empire's intimidating AT-AT™ - All Terrain Armored Transport? Seat the AT-AT Driver and Snowtrooper ™ in the cockpit of this mighty war machine and move the head to aim the spring-loaded shooters. Evade the mighty, stomping legs of the AT-AT ™! ... "
The Set has the same price as the 2010's At-At Walker.