This plugin helps enhance WordPress' default image optimizing if your server is using Imagick (which is preferable to GD if quality is important). There are enough options to dial it in for your particular needs, and the authors continue to add the right options as needs arise.
The one option that is very unique compared to most image optimization plugins is the ability to add sharpening to the resized thumbnails. By default, WordPress does not really sharpen the different smaller 'thumbnail' images it creates every time you upload an image. This is VERY important if you value sharp, quality images, as downsampling images can make them look very soft (this is why Photoshop can automatically sharpen when downsampling). This feature alone is a game-changer for us!
Lastly, the plugin authors are very responsive and helpful, and seem to care about doing things properly.