In most cases, the campaign for the MMXII version of the game is the same as the CE version, so any notes in the walkthrough for the CE should be the same for MMXII. Where we've noticed differences between the two, we've added new comments to the walkthrough.
Early in the game you lose an attribute point (usually vitality) when you die, but you don't lose any experience. After gaining the crystal of life, you won't lose the attribute point, either.
Classes no longer provide learning bonuses. Instead, you simply receive 3 skill points and 3 attribute points each time you gain a level, and you use these points to improve your attributes and skills. The exception to this is weapon skills, which you can also improve by using the weapons associated with them.
Classes do not have attribute or skill requirements.
Skills do not appear to be capped, but you can only raise them to your current level. For example, if you're level 5, then you can only raise your skills to rank 5.
As you gain levels, you automatically learn spells for your default school of magic. This school depends on the class you chose during character creation: Adept - Crystal Magic, Fighter - Rune Magic, Mage - Arcane Magic, Rogue - Nether Magic. For any other school of magic that you start with or gain later, you have to find or purchase the spells.
You can only use equipment if you have the skill for it.
To invoke an item or use a potion, you must put the item into your hotkey bar and activate it from there.
The game now includes more equipment, and you're not required to identify anything.
If you use mouselook mode, then the interface won't tell you when you're next to an object that you can interact with. To see this, you'll have to switch to point-and-click mode (by pressing the control key).
You now regain health pretty quickly, so fireplaces no longer do anything. As a result, there is no longer a way to advance time in the game.