One of my favorite

Clear browsing data with a single click is a great idea but it doesn't work for me. Checked all the extension settings and tried it out multiple times.
Having "Cleared Browser Data" with the extension toolbar button I then look into the Firefox settings and there are still cookies and other saved data sitting under the "Manage Cookies and Site Data" heading.

I re-installed this extension again but it still doesn't clear all the data it claims to.
Nice idea but it doesn't work.

Works ok, however I shouldn't have needed to go on an exploratory web search just to figure out how to add the icon to the toolbar - not the sort of thing I do every five minutes. It would have taken the Dev an extra 60 seconds to include this information. FWIW for anyone seing this in the future, to save you the hassle of looking it up, L-click the little jigsaw piece on the toolbar, L-click the correct addon, L-click the cog and select add to toolbar.

It's amazing. Easy to use.

Finally an extension able to execute what a web developer need to work.

Simple to use. Almost too simple. I clicked on the toolbar button expecting options and deleted all my history, etc. The simplicity is what makes it great. To prevent another accidental deletion, perhaps I should unpin it from toolbar.

good