Microsoft announced that Office 2013 was released to manufacturing few weeks ago and now the RTM build is available for download. People having MSDN and TechNet subscriptions can download Office 2013, Project 2013, Visio 2013, Lync 2013, etc,. If you have previously installed any preview version of Office 2013, you should uninstall it to proceed with Office 2013 RTM installation.
Microsoft said the following on Office 2013 release,
This is the most ambitious release of Office we’ve ever done. It spans the full family of Office applications, servers and cloud services. The new Office has a fresh, touch friendly design that works beautifully on Windows 8 and unlocks modern scenarios in social, reading, note-taking, meetings and communications. We are proud to achieve this milestone and are eager to deliver this exciting release to our customers.