Of course, platforming has been around for years, but I've never played a first person game with such strong platforming elements. The first person view point makes the game very exciting, and the climbing mechanics worked very well in the demo. There isn't a lot of things that you can't climb.
However, there are a couple of downsides to the demo. For one, the demo is incredibly short. On a speed run, knowing exactly what to do, I cleared the demo in under 1:30. If you choose to take the tutorial, and don't know exactly what to do after that, the demo may last about 10 to 15 minutes. This doesn't say anything negative about the final game, I just wanted to play more.
My main complaint with the game is the graphics. Based on the demo, I would say that Mirrors Edge is trying to focus more on gameplay than graphical power. Nothing looked bad, and I'm sure the lack of detail is due to the art style, but I still couldn't help but notice that the graphics were rather plain, and there didn't seem to be a lot going on in the game world. The character models of the enemies weren't very impressive, either. Besides these graphical complaints, I'm very excited to play the full game of Mirrors Edge. It's unique, it's thrilling, and hopefully the levels proceeding the one in the demo will have a sharper look to them, and be equally as enjoyable.