I work on ships, mostly down in the engine room, where it's loud and hot and I'm constantly having to stick my head around piping and equipment to see what the heck I or someone else is doing. I love these little guys because they don't take up any space outside my ears while still having one of the highest noise reduction ratings around. The sizable foam tips mean my little ear canals don't have to deal with excessive pressure from large disposable foamies, and once they've been worn for an hour or two, they actually slide in and out pretty well without having to compress the foam. (Thanks, earwax?)
Only down side is that the foam does wear out in a few weeks of wear, so when I'm running 8-10 hour days out in the noise seven days a week for a month or more on end, I have to take several replacement sets with me. Normal people who only have to wear them an hour or two a day for their jobs should feel like they last forever.
Also, while their being tiny is great in most cases, I'm really nervous about losing one out of a pocket while I'm crawling around on the equipment, either out on deck or down in the bilges. So I made up a lanyard to connect them, and I actually have the middle of it trapped in my ponytail during the day while I'm working. That way when I can take them out of my ears, they stay attached. Don't mind the weathered appearance - I've been wearing these things when underway (or at the range, or on airplanes...) for like a decade and the cord is almost that old.