I really love the new top navigation in the Office 365 technical preview:
You can check your e-mail and easily switch back to SharePoint by clicking at Sites:
You will see an overview of sites added by your administrator (the Contoso one) and the sites you are following. These sites will be filled with sites you are a member of. You can remove a site by clicking at the favorite icon. This is a really user friendly interface and I believe end users will appreciate this.