I have heard that the new art will better match the expansions (particularly Normandy) and with 2 sets of maps you can play the giant scenario in the Designer Series book, but seriously I can't see any reason to pony up for this map pack beyond that, and frankly I don't really consider those minor considerations to be worth the cost.
Frankly I find the maps in the base pack fine as is.
My kitchen table is 4 1/2 feet x 4 1/2 feet, and will be just barely big enough to set this beast up on...where the hell are we going to roll the dice!