At CES this weekend Neowin.net shared some statistics it obtained about Office 2010 beta and Office 2007 use (saying data was created from a Dec '09 beta survey and from Office's anonymous reporting).

o 41 billion minutes in Outlook
o 31 billion minutes in Word
o 18 billion minutes in Excel
o 3 billion minutes in PowerPoint
o In October 2009, US online PC users spent more time in PowerPoint than in Halo 2 on the PC

Not sure how to quantify the numbers, but they are interesting and amusing. There are some more listed here.

- Troy @ TLC