While it does seem to work well, I was unable to get the icon to appear on any of my toolbars on separate computers. And with no hotkey, if you are screen-shooting a few tabs at a time, it's not any more convenient than clicking through the Firefox screenshot option. The only advantage seems to be the "full page" feature which most people would probably use the fewest amount of times.
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Addendum: I was planning on changing this review today, as I reviewed other add-ons I also started using yesterday. Then I saw the developer response, and thought I should hurry before they get any more irate.

I did know about the "pin to toolbar" option for the add-ons. However, when I first tried it, the icon still did not show up on the toolbar. It wasn't until later that I noticed that others weren't showing up either after trying to pin them. So, I removed those add-ons and reinstalled them. Then it worked. This was a brand new profile, so maybe some bug or something that came with an update? I don't know.

As for the shortcut key, I also noticed that the keys for this add-on was in conflict with another key, which I thought was the problem. But after removing the conflict - and then reinstalling the add-on - it still doesn't work. Another bug? I don't know. In any case, I raised my rating to four stars since, as discovered, this was obviously issues with Firefox itself and not just the add-on.