A Very Different Web

More automation potential XML's combination of generic syntax and customizable labels and structures promises to help developers create content which can easily be repurposed along a chain of processors.
More unmediated application-to-application communication The browser doesn't have to be in the way any more, and humans don't have to be directly involved in every transaction.
A new set of architecture and security issues Reusing HTTP scares people, and the multiple transformation capabilities of XML go way beyond the generate-and-present model of HTML development.
Publishing services, not just documents XML came from document publishing, but promises a new kind of service 'publishing' on the Web.