Works very well on large JPEG images. I had to stare at the screen really closely to notice the images were slightly blurry, even when using the highest compression setting. Currently saving 71% on image downloads. Only found two problems: 1. "Convert to black and white" is on by default. I suggest changing this to "off". 2. The transparent background on some GIF and PNG images comes out as black. It would be better if the compression process was skipped for GIFs and PNGs (or at least for small ones, or those with transparent backgrounds).