Every time I try to migrate users at my company from MS Office to OpenOffice, the story is the same. They accept it at first, but a week or a month later, they come back to me and say "Some of my word files don't work right in my office. can you give me the same version that [name] has?" where [name] is the name of a person who still have MS Office 2002 on their computer.
When I try to track down specific complaints, I usually find a subtle formatting problem that breaks a table over a page boundary, or makes an awkwardly formatted page, or a font that ends up making a particular line of text just one pixel wider than it used to be causing a reflow. Stuff like that.
I get *almost* the same reaction from people when I try to upgrade them to MS Office 2007. (with higher emphasis on "I can't find feature X" and lower emphasis on "this document formats wrong")