I just wanted to post a before/after page load speedtest result for a site that went from using Genesis to Generate Press. The change produced a 30% improvement in page load speed!
On the left is the site running Genesis and autooptimize, middle is GeneratePress without autooptimize, far right column is GeneratePress with Autooptimize.
Yes, the actual page size in the before/after process for the older version is larger, but there are actually more than twice the number of images on the new version and I haven’t even run the new images through kraken yet. But once I do, I suspect the page load speed will drop another .1-.2 sec.