I previously grabbed few codes of Shortpixel which is really good. But I like testing new tools especially when there is analytics to show. So I have switched from ShortPixel to Gumlet to give a try.
Setting is quick and easy, you can choose the source type and then you just choose a subdomain for the cdn like name.gumlet.com (I have read that it could be white-label if you spend 1TB/month?) and here we go, it starts compressing/optimizing and delivering images. I have tested with images already compressed and some not compressed and it works well for both cases (it doesn't compress images that don't need it).

It sounds as fast as Shortpixel !

Finally the most important point, the PageSpeed score. I have done few tests with Shortpixel and gumlet. I get 91 for Shortpixel and 93 for Gumlet, almost the same good work.

I think I will switch to Gumlet because it's more friendly even if it's less mature (but I have good faith in Gumlet to be perfect). I just wait few weeks in order to estimate how many stacks I need for the bandwidth.