Adobe Speaks Out on Microsoft PDF Battle
Who really knows what goes on in the negotiations between Microsoft and Adobe. However, this article states a very legitimate fear: Microsoft will extend the PDF format in a way that makes the format a) less useful than it's own XPS format, or b) incompatible with non-Microsoft OSes.
“While much of the press coverage to date has centered on disputes over PDF and XPS [a competitive technology to PDF] in MS Office and Vista, the real issue is the protection of open standards,” Adobe explains
There's no proof that this will happen, and I'm not sure Microsoft would even want that to happen. However, look at what happened with Microsoft and Sun with regards to Java. Maybe that's why Adobe is doing what they're doing, much like Sun did six or seven years ago.
I would love to see Microsoft and Adobe come to an agreement that a) PDF will be a PDF in Office and Vista, not Microsoft-extended PDF, and b) PDF creation can be left in the OEM version of Office and Vista.