Mirror’s Edge producer, Tom Ferrer, explained that the time trial portions in the game will be “bite-sized and short so you can grind them and play them and get faster and faster. It’s not like playing an entire level.”
You’ll be able to upload your times to the online leaderboards. You’ll even be able to download ghost data that appears in the game as a red silhouette showing how other people completed the task.
It’s a pretty cool feature, especially getting to see how other people did it like that you’d be able to learn how as well.