This directory houses surveys (in PDF and other formats) indexing OpenOffice.org use, including patterns of use and numbers of users. At least, that's the idea. Right now, the directory contains one survey conducted jointly by IDC and OpenOffice.org in the fall of 2006 on OpenOffice.org usage. It does not speak to numbers of users.
What does give an indication are the surveys mentioned in the Market Share Analysis wiki. As with all such things, the data are to be taken judiciously.
There is also a continuing survey for developers, created and hosted by Erwin Tenhumberg and Cristian Driga.
Survey: http://oosurvey.gratismania.ro/developer/
Results: http://oosurvey.gratismania.ro/developer/results.php
An analysis of the results from this continuing survey were recently presented at the 2006 OOoCon by Erwin Tenhumberg, in a presentation titled, What open source lovers want? (PDF: 812KB)