There are back-compat features in Word to render files using old rules, so work has been done to help preserve your visual layout across versions.
That said, there's a ton of churn between different versions of Word, so there's no guarantee a bug-fix (or sadly, a regression) won't cause your document to display differently anyway.
FWIW, Word has PDF/XPS export built in as well. (I believe Word 2010 has it in the box, and Word 2007 has some silly downloadable component to enable this).
And, of course, with the free PDFCreator virtual printer on Windows, or the PDF generation builtins on Linux and OS X, there's no reason you can't use PDF from any app...
Not to mention that PDF generation was probably added to word as a response to OO's capability.
Saying OO does the same thing as MS Office, after someone says that Office does the same thing as OO is a bit redundant.
So just to be extra redundant, let me repeat that saving and opening Word documents in Word doesn't guarantee it looking the same (e.g. if you un/plug a printer, it can change the margins and hence the paging of your document) so it's hardly a damning indictment of OO.
If you want to enforce how something looks, you use PDF. That's what it's for. Word's .doc and ODF aren't designed for that, they're more like HTML in that people are terrified of trying to get some simple formatted text to display in two versions of the same Microsoft product, never mind some crazy free software with a silly sounding name. Meanwhile people are somehow managing to send Hi-Def video round the globe and watching it on hardware with the cheapest Chinese chips possible and generally not batting an eyelid because it's based on some kind of standard that's actually worthy of the name.
That said, there's a ton of churn between different versions of Word, so there's no guarantee a bug-fix (or sadly, a regression) won't cause your document to display differently anyway.
FWIW, Word has PDF/XPS export built in as well. (I believe Word 2010 has it in the box, and Word 2007 has some silly downloadable component to enable this).