Via Mary Jo Foley and others, Microsoft is building a PDF alternative with the extension XPS. It's about time. Acrobat Reader has become a bloated pig of an app. It often takes longer to load all the add ins at the beginning than to load the document! I've heard a lot of Acrobat complaints over the last year so I think Adobe is ripe for an assault. But, MS will have to do this right. They'll need Linux, Unix, Mac and Windows clients for this thing to have a shot. Even then, some people simply won't use it because it's an MS product.
The beauty of this model though, is that the creator is in control of the format. There will be potentially millions more Windows users creating content than Mac or Linux users. If MS can drive them to XPS, they have a chance to succeed. The irony of course is that MS is looking to put an end to Adobe's monopoly.