The ability to rewind time for only a few seconds, maybe a minute, would be awesome.
But there is one problem, there would be many many Realities left behind, and many you's since i don't think that it would be possible to just rewind an event without having any leftovers of it. But who am I to make theories about that, I'm not a Scientist.
But if there is a way to control time in a way that makes time traveling possible for a human being and surviving that, i hope it wont be used.
The fact, that Dinosaurs still live if you just look to the earth from many Lightyears away is awesome enough.