A study from Germany reveals that OpenOffice now holds 21.5% of market share, for users in Germany. That's an increase of 3 points compared to last year. Considering the hold Microsoft Office already has, seeing OpenOffice installed on 21.5% of computers is amazing!
The study analyzed fonts in documents published over that time. For example, OpenOffice documents include the Open Symbol font, making them easy to recognize. However, I don't know how precise by analyzing fonts - especially since it's not hard to install Microsoft's fonts on Linux, and configure OpenOffice to use them by default (this is what I used to do when I ran Linux at work, for example.) So I consider this to be at least 21.5%, not an exact number. The study itself puts its margin of error at ±10% for correctly detecting Microsoft office.