Dazed and confused.
There are three games inside Mirror's Edge. One is an awesome and original first-person game that emphasizes on flow and momentum, with a shaky camera that reminds me of the Bourne movies. One is a slow puzzle game, with a focus on platforming, which reminds me of Portal. One is a terrible, god-awful melee-combat action game that requires a lot of trial-and-error and is very frustrating. The first two games are amazing. The last one is dreadful, ruins the good effect of the first two, and just pisses you off.
The story is nonsense. The protagonist, Faith, is a runner. Runners are the only means of transferring information in the futuristic society Mirror's Edge is set in. Something happens, Faith's sister gets framed for a murder, Faith's friends turn out to be enemies, and the game ends in a very underwhelming climax. The story-telling methods used don't help much either. A dude gives you your objectives through a head-set, and he occasionally tells you something about the story. The only other input for story is the super-short 2D animated cut-scenes, which look pretty bad.
On the other hand, the visuals and the art-design are great. Everything has a simplistic and super-clean look. The game looks amazing, in short. It is based on the Unreal Engine 3, which we all know can look really bad. But the way this game implements the engine is just amazing. And you know the infamous texture loading effect Unreal Engine has? Due to its clever use, that actually makes this game look even better!
If anything, Mirror's Edge is novel and original. The designers had a great idea at first, but they forgot what game they were trying to make half-way through. When everything clicks, Mirror's Edge is awesome. The first few levels consist of fast on-foot chases on roof tops, great level-design that let you keep your momentum, and occasional face-off with a foe which ends with an awesome disarming animation. That is what you see in the trailers, and that's what you experience in the demo. The next few levels see the addition of the puzzle-platforming sections, which are pretty well-designed, but require a lot of trial and error. Luckily, the checkpoint system is very forgiving in these parts. And then, the game adds the sections where you have to take on a bunch of machine-gun wielding foes at a time. These areas suck the life out of the game. Whenever Mirror's Edge gets going and you feel like you are Mr. Jason Bourne himself, one of these section pop-up to remind you that you are just a weak teenager girl. Now don't get me wrong, I love unlikely protagonists; I loved Thief. But in Thief, the AI was dynamic, and you could avoid encounters with enemies due to most levels' open-ended design. But the fighting sections in Mirror's Edge are super scripted and mostly happen within confined areas, and there is no way to avoid them. The designers either had to make the main character a bad-ass (Jason Bourne anyone?) or they made it so that the fights were avoidable.
There is a mode in the game, called Time-Trials, that takes out the hassles of the foes and just let's you fly through the levels as fast as you can. It's a breeze, but since you have no rivals and no real motivation, I doubt you will play through the maps more than a couple of times. If they would've enable racing with human-opponents, that would've been great and that would've extended the shelf-life significantly (the game is selling for 20-bones only six months after it's out).
Mirror's Edge consists of two parts excellence, and one part feces. If you have the patience to shovel through the feces, you will appreciate the novelty and the originality. There are lots of great ideas in Mirror's Edge that are mixed with a bunch of not-so-great ideas. It seems as if the designers were confused about what game they were trying to make. I hope that the team gets a second chance to iterate on the great ideas one more time. There is also a sense of inconsistence quality throughout the game. There were moments during the game that I swore to myself that I will give Mirror's Edge one-star, and there were moments that I thought I was playing a five-star game. Mirror's Edge is a mixed-bag, and I usually give mixed-bags three-stars. But Mirror's Edge is daring and different in a world of generic-ass-shooters, so I will give it four-stars.