true progressive mode actually gives you something usable before it's fully loaded, to the point where "not fully loading" can be entirely acceptable. If all images load "first iteration" first, you have a stable DOM that won't need to reflow in any way as each image goes through the rest of its progressive layers. And having a nice setting that says "only load up to X on slow networks" and "require image click to load past first iteration" would be godsend, even on gigabit connections. If I could bring the size and load time for modern webpages back down to "maybe a few 10s of kb" and "immediate" rather than "2.9MB and a second or two", I'd happily turn those options on.