I tried the demo. The PS and the TB one.
- The results with pingdoom and google pagespeed is that there is no difference (some times a little better, sometimes a little worst so i would say it is simple aleatory due to servers). This can be because the demo website is very light and with only a few products, but i hoped something would improve.
- Lazy load, that could be the thing i can visually recognize, i can not see how it is working. Usually with lazy loading you can see how images load if you scroll down very fast. here I can not see that.
- Pre-connect: i see this is reflected in the code with option is on. But I was not able to check with any tool that really improve performance.
- Image dimensions: very interesting feature. I know i have some images with this problem because i saw it with some tools (gtmetrix i think), but I am not sure how to test if this works of not since the demo usually is well constructed and there are not missing things.
- preload images: not sure how it works so I will not evaluate it.
What to say, I think the module have interesting features but I could not proof any of them to have a real impact (in the demo store). Maybe It would be more evident in a shop with a lot of products, images... who knows. Maybe I will try it whith my new web when it is done and see how it can impact a more "heavy" design.