Obviously there's a wide spectrum of possible uses and different people have different "focus" tastes. I've found Firefox's PIP particularly useful in watching videos while grinding in certain types of MMOs. So long as the MMOs support "Borderless Window Fullscreen" rather than "pure" fullscreen, Firefox's PIP shows up right on top. I just recently upgraded to an ultra-widescreen so I've got plenty of horizontal space to play with. In a previous dual monitor setup I might have just had the game on one screen and the show on the other. This PIP gives me a bit more flexibility than that, especially I discover which games sing in the "2k" fullscreen. Some of these MMOs I didn't realize quite how cramped they felt in 1080p until I got to extend them to ultra-wide.

I like more than thought I would. I can keep going through tabs without losing the video.

The problem for me is it doesn’t have controls past pause and play. If I want to back the video up or skip it forward I need to go figure out which tab it’s coming from, and I can’t remember if I have to unpop to get controls. Windows 10, ymmv.

This also annoys me. Even just allowing arrow keys to seek back and forth would be enough for now.

That can be enabled with media.videocontrols.picture-in-picture.keyboard-controls.enabled toggle in about:config.

Woah that's perfect, thank you!

Also, the controls have changed: a single click doesn't pause the window as it normally does. Why change?? :/

i use it when i'm watching a youtube or other video that has interesting parts, but also lots of fluff. PiP lets me do other things and mostly ignore the fluff