Wow! One thing that many people have pressed for over time is open file formats. In a lot of ways this argument is more important to governments and large organisations than any debate over proprietary vs open source software.
Having an open file format means historical data will never be lost just because a chosen software package becomes abandoned by its vendors. Having an open file format means you can opt to use Microsoft Word if you believe it offers a familiar and rich user interface for millions of non-technical computer users. Or, you can opt to use Open Office if you believe it gives you greater choices, not to mention it costs nothing.
Microsoft have obviously listened to this; firstly the Open Office XML specification as used by Office 2007 has been published since the beginning but now Microsoft have made public the binary file formats as used by previous versions of Office.
These are obviously fascinating to developers like myself, but very quickly prove to be complex. Joel Spolsky provides interesting commentary as to how the Microsoft Office file specifications evolved.