The latest Microsoft Office 2011 release for Mac OS is creating a lot of the wrong kind of buzz on the Net.
Apparently, the Outlook portion was not as well-integrated or as well-tested - failing to open Outlook databases without a rebuild of the full Office database. The problem is widespread enough that Microsoft had to create and release a support document that provides step-by-step directions on how to get Outlook up and running. In fact, the support document "fix" was released the same day as the upgrade, suggesting that this wasn't some unknown error, but a decision to release a version incompatible with previous Outlook datasets.
Whether this was an attempt to push more computer folks to Windows, or an attempt to trim costs (or keep to a tight release schedule) by failing to include a database translator, or ensure that the software was backwards compatible, is unknown. But it never helps your image to provide a clunky product - particularly one that makes users have to first find out what the problem was, and then have to go through a lengthy process to fix it.
Source - Undoing the damage wrought by Microsoft's Outlook update, Macworld Business Center