I am an Information Systems Manager at Washington State University, where we are implementing a MediaWki 1.4.7 site as a general tool for teaching and learning. Our first pilot/production (we can never seem to cleanly separate the two!) will start in August, 2005.
We are using a "giant fishbowl" access model, which is world-readable, but restricts editing to authenticated users. All (unprotected) pages are editable by any authenticated user; there are no "rights" over particular pages (yet).
We are looking to bring up 1.5, but probably not until the Spring Semester (January 2006).