I just do software dev, but cp with reflink is absolutely killer, and the only reason I don't just go with ext4. Unless I'm crazy, ext4 doesn't seem to have any simple copy-on-write feature I can use to copy/paste an entire project directory instantly. I sometimes do that so I can have two instances of the same app running at the same time, on different branches. I've also used reflink in automated tests, testing a tool that relies on and changes a project's file structure. I can just duplicate an entire dummy project, operate on it, then throw it out and it's fast since it doesn't need to copy bit-by-bit.
