I made a game to fight against the AI just to test out some of the Terran changes, but the only AI setting was "Very Easy." On a map designed for six people it didn't even expand beyond a single base and had gotten a few Hydrolisks up when I was invading with Battlecruisers and Thor.
Thor is awesome, by the way. The only thing that annoys me is his Arnold Schwarzenegger voice and the fact that the lighting inside the thing makes it look like he's at a rave. But the ability to stun and deal hundreds of points of damage using their special ability makes them my favorite new unit by far.
The also have a buttload more quotes implemented when you keep clicking on your units (at least for the standard Marine, who was the only one I tried it with).
Ultimately it looks like it's changed a lot more about the game than I was expecting - I had it in my head that they didn't want to do much but add a new super unit or two, but lots of stuff about the Terran tech tree seems different. Missile turrets no longer act as detectors (there's a separate unit for that), flame troops and Vulcans are merged into one unit, and you can use your communications upgrade at your command center to add a one-time permanent bonus of 8 supply to a supply depot. It's neat stuff, and I'm going to have to look into how the other races have changed.