Microsoft is trying to push new file formats that are using ZIP and XML. Are those new file formats any good for Office developers ? In other words, should anyone feel safe to make direct access to file parts, and start getting free of running instances of Microsoft Office and its COM object model, usually through VBA ? Microsoft does not run out of teasing. There is ton of videos, see here, and here for example, screencasts, articles and blog posts (self-serving Microsoft blog posts mostly) about how much they are opening up. They insist on the fact that, provided you make a valid use of the XML, pretty much changing the content of anything in an existing document can be achieved by sequentially 1) unzipping the content 2) making appropriate changes to one or more XML parts that are compatible with the provided XML schemas and open packaging relationships 3) zipping the content back . Let's see if that's true.