Major item your users will notice are the design/layouts. All the navigation moves to the left side and the main sections become 'tabs'. Once our users got used to that, they loved it, prior they hated it. I would recommend making your app more set for the users, IE if they dont use a section remove it, if they dont use an entity, remove it. The terms are really area and subarea, you can do this from the Customizations section > Solution > then add the app (CRM Hub) or a custom one.
