Confirmed/rumored consumer features in WP8.1?

We have learnt a lot about new features that are relevant to developers, but a lot of the new stuff thats relevant to consumers is not yet included in the leaked build.

So what do we know about these so far? Do we know any details about cortana and smart search that are more than just speculation? What about the start screen and customization?

I made this thread because i want to get a clear realistic idea of what the wp8.1 experience will be like