The good
• Attractive GNU General Public License version 2. This means this add-on is owned and supported by a friendly not-for-profit community. Instead of a for-profit corporation. And more secure because its full code is publicly available for review.
• Easily and quickly set default zoom either per-site or per-tab
• Fast and responsive
• Lots of configurable options
• Add-on can be activated or deactivated without restarting Firefox
• Implemented using the new WebExtensions API. Which is the future of add-ons.
• Available for both Firefox and Chrome with identical functions and user interfaces. So one easier learning curve :)
https://chrome.google.com/webstore/detail/zoom-page-we/bcdjhkphgmiapajkphennjfgoehpodpk
• Friendly and fast support from author

The bad
• After you click on the toolbar button, the text on the following 3 buttons overlap the buttons: “Reset”, “Auto”, “Reset”. Which make those 3 buttons both hard to see and use. But the buttons are still usable. The author said there is a fix in progress to resolve that.

Note
• This is now fixed with version 6.3+. With the previous version 6.2 at “about:addons” under the add-on “Preferences” page the location of the configuration of options might be hard to find for newcomers. Because to find those the user has to scroll all the way under the very long add-on description text :( In my case, after an initial configuration I seldom need to change those configurations though. So it is still usable :) I suggest to keep the add-on description text concise. And move the long details to a webpage. Such as the add-on homepage at https://addons.mozilla.org

Then add link(s) from the add-on “Preferences” page to the add-on homepage. I understand Mozilla made a poor usability choice by moving the configuration to that location. But I’m assuming the developer has control over the lenght of the text and can add URL into that description of the add-on “Preferences” page? Any other suggestion to resolve this challenge?

Using
• Add-on version 6.3
• Firefox 52.4.0 (64-bit)
• Debian 8 Jessie 64-bit
• GNOME