A Google Image search result click, will show up a preview, to view the original image from there. This feature is useful if you are searching for an image and the related images on the right would be helpful. Google Images has changed the display of the image preview with its new version of the layout. The new design is good, as it dynamically gets the preview of each image. Sometimes an extra click to get to the actual image can be a work that is boring and unnecessary step. This is the reason for the existence of the user script – Google Images direct links. It has been installed more than 120,000 times which says a lot – that people are not yet ready for the new change or wants to avoid an extra click.
For a designer who looks for royalty free images constantly this script would just get him or her to the picture without all that preview goodness. This would explain, though it is an easy click to get to the original image, that the script has been downloaded 120,000+ times.
Another feature this script targets is the old layout that people are not willing to let go and adopt the new one. They would get the old layout every time when they do an image search with this script automatically, instead of scrolling down every time manually to wait till all the images are loaded on the page when they click Switch to basic version (always).
As for me, I have this user script on, in the times I am bored of the preview. It is easy to switch greasemonkey off, and have the current layout.