I really love the new top navigation in the Office 365 technical preview:
Depending on your administrator status and licenses you will see more or less items. The great thing is that you can go to your Inbox (Outlook) and still maintain this navigation:
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.
Office 2013 is disappointing for me personally. Three years and all they could come up with was moving navigation along the top like Google has had forever? Looks like more of the same except now you are expected to lease it (365) and not own it (2013). My cheap company will stick with 2007 anyway so 😮