For bugs in Firefox Desktop, the Mozilla Foundation's web browser. For Firefox user interface issues in menus, developer tools, bookmarks, location bar, and preferences. Many Firefox bugs will either be filed here or in the Core product. (more info)
Since it seems to me middle-clicking on the Firefox scroll bar in Windows does nothing, I think it's useful to set "middlemouse.scrollbarPosition" true by default also on Win builds. That is also more consistent with Linux builds.