I’ve got to agree with Sam and CNet. I just can’t get too excited about Office 11 and its XML support. XML is syntax, a context free grammar. Standardized syntaxes are wonderful, but heck, it’s just syntax. And while a published schema would describe some data semantics, it would still leave loads of wiggle room for the format to remain proprietary.
I think it is useful, as it does open up the format to XML tools like XSLT. But any use of tools with the Office XML format (such as XSLT style sheets written to manipulate it) will be locked-in to the Office 11 format, the same way that software written to the Win32 API is locked-in. That’s not an inherrently bad thing, of course, but let’s call a spade a spade.