I’ve tried them all, and Squash is the only optimizer that doesn’t make the image darker nor desaturate the colors. Critical, IMHO. Bravo.
Suggestion for version 2.1: allow a user selectable smidgen of sharpening to the final image. A slider would do to control it. (For comparison, Smush does a good job of adding a bit of crispness back, but suffers from the darkening issue.)
Nice job, guys and gals.