The summary statement glosses over the value of a highly structured portable XML document. A value that goes far beyond the strict separation of content and presentation. The portable document model is the essential means by which information is exchanged over the Web. It is the key to Web interop.
Up till now, Web docuemnts have been very limited. With the advent of XHTML-2, CSS-3, SVG, XForms and CDF (Compound Document Framework for putting these pieces together), the W3C has provisioned the Web with the means of publishing and exchanging highly interactive but very complex docuemnts. The Web documents of the future will be every bit as complex as the publishing industry needs.
The transition of complex and data rich desktop office suite documents to the Web has been non existent up till now. With ISO approval of MSOffice-OOXML, Microsoft is now ready to transition billions of business process rich "office" documents to the Web.
This transition is accomplished by a very clever conversion component included in the MSOffice SDK. MS Developers can easily convert OOXML documents to Web ready XAML documents, adn back again, without loss of presentation fidelity, or data. No matter what the complexity!
The problem here is that while MSOffice-OOXML is now an ISO/IEC International Standard, XAML "fixed/flow" is a proprietary format useful only to the IE-8 browser, the MS Web Stack (Exchange, SharePoint, MS SQL, and Windows Server), and the emerging MS Cloud.
Apache, J2EE, Mozilla Firefox, Adobe and Open Source Servers in general will not be able to render these complex, business process rich, office suite documents. MSOffice-OOXML itself is far to complicated and filled with MS application-platform-vendor specific dependencies to be usefully converted to Open Web XHTML-CSS, ePUB or CDF.
XAML itself is only the tip of the iceberg. The Microsoft Web Stack also implements Silverlight, Smart Tags and other WPF - .NET