I like this. Simply switch zoom mode. So I set a Firefox original scale toolbar button beside the button this provides. This is enough. Even complex websites have no side effects.

Absolutely essential addon if you hate small text, but get problems in various websites where the entire page does not show, or the page is too wide to fit your screen. It's especially handy when viewing data columns, like on Wikipedia, and the page won't show the entire column because your font is too large. Flip this button and suddenly you can zoom the text in the column. Flip it back when you need to without going into the Settings panel.

This extension simply does not work. When I am on a text-based homepage, I can click on the icon of this extension as many times as I want, but the text does not enlarge. How to build a Zoom Text extension correctly can be seen in the Chrome extension Zoom Text Only.

Would be perfect if it indicated which zoom it is set on, text or page. The having to guess is a waste of time and energy.
AS I said would be perfect IF.......
Firefox desperately needs this.