Audiences vs Permissions

That was always unnecessary. You add the share permissions to users in the app which is now on the "Manage Audience Access" section.

So if everyone should be the same, just add the groups (or emails - bad idea as it is an administrative nightmare to keep up with, but you can do it) to the access settings, then check other optional settings (sharing, build, etc)

Note that anyone with permissions to the workspace will override this. So if Joe is a contributor and can share a report and dataset for his reports, it will override for Joe the fact that it is unchecked in the dialog box above.

If you have some users you want to be able to share and others you don't, that is where this new feature shines. You simply create a new sharing audience with share permissions in the app, and deny share permissions to the rest in the other audience.