Rated 4 out of 5 stars
Great add-on, but changes to print.tmp.* need to be whitelisted. Even after including .*:print\.tmp\..* in the whitelist, Preferences Monitor continues to create multiple alerts when printing.
The developer says that '.*' can't be used, even though it's a valid regex. Since 'print.tmp.*' is changed "by" the site you're attempting to print content from, it will have to be whitelisted in the extension itself. This happens regardless of whether the user invokes the print dialog manually or presses a "print" button on a page.
.*: is not valid, it have to be the (case-sensitive) name of who is changing the pref.
Rated 5 out of 5 stars
Amazingly useful! I've used this to diagnose misbehavior by "good" add-ons that try to change proxy settings invisibly, and other well-intentioned uses.
Would be nice to see regex matches made case-sensitive, but I'm keeping it either way.