Office is the number one reason why many companies wont ditch Windows for Linux.
Open Office made some inroads, but most workers prefer Office. Outlook is also by far the most popular email client used in big companies. The Linux alternatives aren't on par with Outlook because they don't communicate well with Exchange Server which is already in use by most big companies.
I refused to move the desktops in the company I worked at for the last four years to Ubuntu, specifically for these reasons. Linux on the desktop isn't ready for big corporations, mainly because of the lack of Microsoft Office.