Microsoft's Office 2013 reaches its public Customer Preview milestone today, available for end users to test on Windows 7 and Windows 8 PCs. Microsoft is calling its Office 2013 suite, codenamed Office 15, a "modern" version of the software that is used on a billion PCs worldwide. Cloud-connected and designed to work well on Windows 8 tablets, Office 2013 signals a shift to document collaboration and anywhere any device access. Notably, Microsoft is introducing an on-demand subscription version of Office 2013 that can be streamed from any Windows 7 or Windows 8 PC, with the ability to sync settings and documents. With strong competition from Google Apps and Apple’s iCloud storage and iPad hardware, how does Microsoft plan to keep Office 2013 desktop software and its cloud offerings relevant in a multi device era? Read on to find out.