The problem I have repeatedly experienced is that SharePoint adds one more place to maintain. For me the place where I/we keep all and most of the documentation is TFS. We keep track of user stories, deliverables and bugs. We are learning to use Test Manager, although we now slowed down because we are waiting for 2012 which will do some of the things differently.

Then there is e-mail. People keep e-mails with pieces of important information, but not everyone was on TO or CC. So if the question pops up again later, someone has to find the old message and forward it to the newbie.

So SharePoint just adds a third method of documentation storage. I would use its wikies, not the storage of Office documents.