Of all of the things that have been added, the most useful is the Notification Center. People will stop using Cortana about as quickly as they stopped using Siri. File Manager is useful, but only when you really need it, which wont be often.
Belfiore seemed to say "balancing act" a lot. I do believe what he was saying, but in a lot of ways it means "we tried to do things to make everyone happy, and some people will never be happy, so we tried to meet down the middle". It was good for him to try to build some buzz for the product, but a lot of the questions were centered around why some things are missing or why some things don't work the way we want them to. I wonder what kind of buzz was really generated by this AMA.