Every time I see that Firefox has made an update I get a feeling of dread wondering what other portion of the (Good! Useful! Functional!) UI that you're going to mess with next and make worse in the process. Additions are fine, as long as you have the option to disable them. Changing something in the UI that already exists is loathsome and it can take hours or days before someone figures out how to us CSS to revert the unwanted and unasked for change you've made, if they even can.
