The list of features and changes in the expansion is right on the nose, I expect great things from this franchise in the future.
The only dark point is the Steam-only thing. Don't get me wrong, I use steam, but whenever I have a choice not to, I don't.
Before the Steam fan-boys jump all over this, consider this. The people who under no circumstances want to install steam on their computers, are not pitchfork bearers shouting "burn the witch", erh... steam. Quite the opposite, they are quite computer savvy and have quite a few valid arguments. So sarcastic comments about grandmothers excommunicating AD&D aside, maybe you should pay a bit more attention to them.
From a layman user standpoint alone, the Steam client is clunky, buggy and cumbersome. It has gotten better, but it still is a pile of garbage. I understand the convenience it brings to developer, and it is borderline convenient for the user too, but locking all your software in one platform ? I don't know, it sounds much like putting all your eggs in one basket.
It all boils down to the "adapt or die" philosophy. You see, "adapt or die" is not about freedom of choice, because dying is actually not a choice for any sane person. It's pretty much equal to "your money or your life" - exactly what choice does the gun-bearing mugger give you ?