=== Which pref are really used ===
In order to clean up the UI (as Firefox do in Fx4), we need to know which pref have been changed by the user from their default value to a new value. This will allow us to track the prefs that are maybe not understandable or never used.For instance, do the user care about "marking the junk message as read" pref?
=== Other places we've asked ===
[http://breakingtheegg.tumblr.com/post/7087898858/mmmm-test-pilot-for-thunderbird-so-what#disqus_thread The Thunderbird UI Blog]