Microsoft believes that a move to XML will make for better data recovery, and will also boost security. It is now possible, for example, for files with hazardous code to have the malicious portions spotted before execution. Office applications will also have greatly increased interoperability because of a move to XML.
The formats will improve the sharing of information for collaborative projects and augment corporate workflows. The new file formats will help applications access documents and spreadsheets without manual entry, boosting worker productivity.
Moreover, the formats come with a royalty-free license, meaning any developer can integrate them with their tools without paying Microsoft.