Since I'm just in this thread again anyway: If that was your experience with lazy loading images I can relate, and understand where the negative impression is coming from. That wordpress script is probably loading the image only when the DOM object becomes visible, which will always cause the loading process to be noticeable. Shortly on good connections with small images, so it won't matter much there, but that experience gets worse for slower connections and bigger images of course.

My background that made me write the comment above is that I implemented lazy loading for a feedreader in JS, with predictive early loading to exactly avoid this problem, and I did test the browser feature just recently again. In those scenarios lazy loading really does work well enough for my statement to be true, according to my testing. For common connection speeds and image sizes only of course. Though I'd argue it also helps in less optimal scenarios exactly because it somewhat decouples the image loading from the page load - that that overall experience was horrible on long threads with many images in the feedreader was why the lazy loading feature was added, the contrast was stark.

I should have defined that better in the comment above and given your experience more validity. Next time :)