I generally like this add-on. But be aware that it creates a keyboard trap in all textarea fields. This prevents you from being able to use your keyboard to exit a textarea field with the Tab key. It would be nice if there was a special keyboard shortcut to exit a textarea field.

It works great when I need it. But there are some webpages where I do want to use normal (shift)tab functionalities. A domain (or full url) white-/blacklist (supporting regexes/wildcards) would help to distinguish in this.

Another solution would be to have 'shift tab' (optionally) not work when there's nothing selected.

Really nice add-on but it would be nice to have the option for the number of spaces in tabs.