when we went at Christmas-time a few years ago, we stayed at the Wilderness Lodge and LOVED their decorations. We also found secluded locations with fireplaces and couches that you could look down onto the lobby from. Get a drink from the bar, head to one of these hidden gems (a few floors up above the main entrance doors) and enjoy!
If you have time, go over to the campgound and take a ride around (rent a bike, take your car, take a carriage ride, whatever). Those who camp there, especially in RVs, go ALL out in decorating! Its amazing the amount of decorations they can fit on a campsite (think lights, blow ups, trees, animated figures, etc). Its really cool.
Also, we loved taking the monorail to the resorts on that loop - what awesome decorations at Grand Floridian (the giant gingerbread house) and the Polynesian (a Hawaiian flair!). We didn't make it over to the Boardwalk resorts or AKL but LOVED all of Disney at Christmastime.
ENJOY!