Excellent addon. Really improves site performance on image attachment heavy pages. I use jpegoptim quality 90, and the results are fantastic. I really appreciate the options to keep all metadata (EXIF, copyright, etc), and it works well with AndyB's Convert All addon.
The only issue I had with this addon is that it massively increasesd server load wihle churning through the hundreds of thousands of attachments on my site. After that first optimization, it does not have a significant effect on server load while it continues to optimize new image attachments on an ongoing basis.
I bought 7 licenses and am using it on sites which have up to 500,000 large images each. Works really well!
Great support and nice addon. It does what it announces, in my case: Saved 27.83%. Total capacity (old): 306.6 MB and new: 221.3 MB
Developer helped through my own server and helped to make it run without problems. Totally recommended.