Of course, Google Docs/Open Office also have a role to play here. Microsoft is slowly but surely losing it's hegemony.
It's easy to point at all of the new Office competitors and say MS is doomed, but none of them have any significant market share yet. OOO has been around forever, and even Google Docs and Zoho are past the stage where we'd call them new.
As for the various office productivity packages - sure, they've been around for quite some time now without really making much of an impact, but things starting to change. Firstly, Microsoft dropped the ball on the Mac platform by dropping VBA support for the Mac. If you want to use VBA on the Mac now, the best option is OpenOffice, not MS Office.
Secondly, those packages have been steadily improving - for me, it's only really been in the last year or so that OOO has got to the point that it could be considered a serious competitor to MS. You have surely noticed the massive discounts that MS has had to give for Office to keep it installed in large organisations recently - there have been plenty of examples in the press.