Being a big fun of Teams, I was particularly amazed by the new functionalities. The biggest improvement is the User Experience.
From updating the document properties, change the lists colour formatting, to have a full experience around document co-authoring, I think Teams should be now the corporate core tool.
I particularly like the permissions demo,
When trying to share a file with someone, Teams prompt you to grant access to anyone who does not have actually access to the file and can also create a private discussion if the person is not in the channel