Heroes can now be assigned companions from your character pool. This is accessed through the hero UI, which is in the context-dependent pane to the right whenever you select a hero.
Also the foundations for character skills has been added, and more work done on merging character/hero systems. In a patch or two a Hero will be a character with the “Heroic” trait. The fellowship functionality is also close to done, so you can have a larger group of heroes and characters and send them on epic quests or into dungeons in search of loot and forgotten lore.
WinXP users get .NET 4.0: http://www.microsoft.com/en-us/download/details.aspx?id=17851 instead of 4.5.1 (which is not compatible with XP).