User can't select which images to extract. It's just all images in a document. For most image processing and approval workflows, that can easily be hundreds of images, when you just want to extract and make notes on one. Of course, the free version is the first 4 images in the document, so it doesn't help there.
Also, this extension seems mysteriously focused on removing the images from a document, rather than saving them off.
It does what it says it will do. It just seems like it needs a few changes before even the paid version would be useful.