Do not use this extension. It is incompetently written. If you have the Firefox setting "Always ask you where to save files" (and not "Save Files to "), then this extension will launch a separate dialog window asking where to save the image, for each image on the page. That typically means that hundreds of dialog windows will be launched all at once, possibly slowing down or even freezing your computer. No, I'm not kidding. Yes, this really is an extension that will launch hundreds of dialogs at once.

The reviews granting more than 1 star are probably from people who happen to have the "Always ask you where to save files" setting. If you are curious, install the extension to confirm what I say, and then give a 1 star review to protect other people from it.