The video shows off several web pages with complex CSS animations that run at a reasonable FPS in Servo, but run at less than 1 FPS on current browsers. These pages were created specifically for this purpose, but that's the general thrust of it: it's not so much that you _want_ your pages rendering at hundreds of FPS, but that you can get more complex things done in a reasonable FPS. It also proves that Rust code can be _fast_, which is always something that is important for systems languages.

I know much less about this aspect, but I also understand, vaguely, that there are battery savings here as well? When you can get things done quickly, you can idle the CPU again, saving power. I believe that's the thrust of it.