1. You can actually own Goldenglow Estate, you also have the option of keeping the surviving Mercenaries (if any) on to serve as guards, for a price, or dismiss them.
2. You can actually become a true Forsworn, as in all Forsworn become allies, there's also a Forsworn quest line.
3. The Bard's College quest line is expanded upon.
4. The Akaviri Dai-Katana is introduced to Skyrim.
5. Ability to wear robes only currently available through console commands, e.g. Psijic Robes.
6. A new light spell is introduced which does damage to vampires, although the higher the rank of the vampire the higher resistance to it they have.
7. Improved realism of weapon effects, e.g. dismemberment of limbs
8. A rework to the Dark Brotherhood quest line making it possible to save the Falkreath Sanctuary, or at least its members, if action is taken quickly enough.