It's not very common for an established industry leader to trash competitor; that kind of dirty politics is usually considered below them. This week Microsoft decided to buck that trend and create what some have called an attack video where customers lament their experiences with OpenOffice.
Microsoft actually has some very valid arguments for their customers staying with Office. The video points out a few of the specific issues that users and organizations will face if they try to switch to any other product. Training is one problem, obviously; most users have some basic understanding of how to use Office because it's what most companies have been using. If anything, Office 2007 weakened Microsoft's position on that point because it requires a lot of relearning. Companies still on Office 2003 are still plentiful, and perhaps these are the ones Microsoft is most worried about when it comes to OpenOffice defections.
Document conversions are far from ideal -- heck, it's a crapshoot as to whether a document will convert between different versions of Office! The more Office features you use, the slimmer the odds that your document will come through to OpenOffice unscathed. Probably the strongest point in the video is about Excel macros. They are a powerful but obscure style of programming. I once wrote an entire expense reporting system in Excel that faithfully recreated a printed expense form. That's not going to convert. If your company has a bunch of Excel "apps" like that then you will be using Office far into the future.
So although every statement in the video is probably true, those are the exceptions and not the rule. By far, most users are not exploring the obscure feature spaces of Microsoft Office. Instead they are writing lightly formatted documents that are only a few pages long, static presentations filled with nothing but bullet-pointed text, or simple spreadsheets that sum a few rows and columns. If you're given the job of deciding whether an OpenOffice migration is possible, you'll need to determine whether the exceptions in your own organization are manageable.