Critical issues of opensource deployment in most office is change management and back office (support). I've been using OpenOffice.org for almost 3 years (or is it 4?) but it's hard to deploy this in the office, even to my own department.
I know that there should be a culture shock the first time they use this application. They keep asking "How do I do this, as Microsoft Office does". Lack of support from the IT function shall shift them back to old application.