The latest edition of Official Playstation Magazine revealed that DICE's platform of choice for Mirror's Edge is the PS3. DICE revealed the the PS3 will indeed by the lead platform for the game.
The article also reveals the future of Mirror's Edge will be in some upcoming downloadable content and Trophies will be supported with the game. Xbox 360 gamers will get trophy-ported achievements, in other words the achievements will have the same specifications as the Trophies but you earn points instead.
No solid info on the DLC was announced, but expect to here more closer to the game's release.
See, PS3 owners have a heck of a lot to look forward to.