Mirror's Edge is the story of Faith, a runner in a near-future alternate reality that resembles a combination of present-day San Francisco, Aeon Flux and The Matrix.
Runners are basically messengers.
In this world people have developed an Orwellian paranoia toward electronic communication (even Google!) and any information important enough to be sent from person to person is now sent via runners, like our female protagonist.
Of course, the paranoia gripping the populace isn't entirely unfounded as Faith finds herself under attack by mysterious government forces throughout the story, presumably for the information she carries.
Thankfully Faith isn't your typical high-school dropout UPS employee. She's equipped with a wealth of acrobatic maneuvers likely to trigger fond memories of the chase scenes in The Matrix in both players and anyone watching the ballet of kinetic movements unfold.

As I said above, the game seemingly echoes key facets of The Matrix, and what would The Matrix be without its omnipresent "Bullet Time" effect?
In Mirror's Edge, Faith uses a similar ability called "Runner Sense" to both highlight the best routes through the city and, of course, to slow time when convenient.

Some of you might be asking yourself: "If she's pursued by armed policemen, can't she just shoot them?"
The government agents of course carry projectile weaponry, but Faith must rely first on her ability to dodge, pirouette and dive out of the way of her pursuers, and if that fails, she turns to an amalgamated form of martial arts that relies heavily on the same acrobatics she uses to navigate the rooftop environments she finds herself running through.

If the enemy proves to much though, she can pick up weapons, but they most of the time just hinder you. Balance -key element of the game- is harder, Faith is exhausted faster, it takes more time to climb walls, etc. So it might be better to throw them away after a few shots.
Alarmingly, all this is accomplished with a traditional first-person view of the world.
If that sounds like it might be a bit disorienting, particularly while flipping over fences or kicking sub machineguns out of the hands of Rayban-wearing suits, you're not entirely wrong.
The entire game is designed to give gamers a "feeling of motion" in both the available actions and the constantly swaying screen, so while motion sickness is an initial concern, your eyes quickly adjust and eventually the experimental view proves engrossing and adds to the tension in the game's fight-or-flight scenarios.
Currently, my only fear for this game is that Mirror's Edge might trip over it's own hype, such as Assassin's Creed, but even then, the graphics themselves are a reason for this game to be experienced like a kick in balls.
This game isn't a collection of pixels, this is a reminder of how good art can be. And this is art.

I'll keep my fingers crossed till it's release, hopefully during 2009, and I strongly advice you to join me.