Seeing nobody else has mentioned it, I guess I will.
Two words: Not much.
Ryan Kunkle from Lionel waved a "U36C" around briefly, didn't even take off the foam protecting the handrails. Mentioned the only difference between a U33C and a U36C is 300 horsepower. Externally, both units are the same. No questions about scale wheels that I could hear.
MTH's Andy Edleman talked briefly about the new fishbelly hopper with peaked ends, but displayed a pre-production standard rib-sided hopper with peaked ends instead. Go figure... Image is cropped from a screen capture of the presentation:
The catalog shows the fishbelly hopper, so, who knows what will be showing up. Stay tuned. Image: catalog screen capture.
Speaking of catalogs, Doug Peck indicated on another forum that there was a rumor that there will only be the on-line S Scale catalog, no hard copy. Also, "Order Now" pricing expires December 1st. Perhaps the catalog will show up after 12/1, given that S Scale is the only MTH catalog with pre-order pricing.