I’m currently catching up with the new TV version of The Flash. (See what I did there?) Nice, fun, lightish show, especially watching it back to back with Arrow. Being a solo TV show about a superhero with one easy-to-grasp power, the writing team are doing their best to show interesting and fun uses for super-speed. It’s one of those powers that you think about as a kid, so it can provide a lot of ideas.
In games, it can get a bit tricky. How you determine initiative, multiple actions and the like, when one of the PCs can run at the speed of sound, or even faster? Celerity in Vampire is enough trouble, and that only makes a PC two or three times faster than usual! How do you stop a PC from going X-movies-Quicksilver on a room full of people before the other PCs get a single action - fun on screen, maybe not at the table.
The TV version gives him super speed but only intermittently super reflexes, so he still has “lag” when reacting to things - he’d only have improved initiative when powered up, and can’t go at full speed all the time.