SPOILERS
How in the world would a trained professional killer not have his an amateur with AT LEAST one bullet during the train scene at the end? But the amateur hits him? Please...
You can see the bullets in the door that didn't quite penetrate from Cruises gun that he got from the cop. Foxx'es gun was the assassins gun, you can bet he was probably using armor piercing rounds, so I'm willing to suspend my disbelief on that.
It's not a bad movie, but between the look-how-cool-I-am director kitsch, the easy-way-out plot devices, and all of the coincidences, (yeah, like you're going to lose cell signal in one of the busiest business districts in the world)
Ugh...I know EXACTLY where that building is, and having stayed in the hotel close to there let me tell you that the cell reception was crap. Besides, he ran out of power.

That said, there were some plot devices that needed too much thought for an action flick. As for why not drive himself, they explained in the movie that he uses the crazy-cabbie as his cover. He doesn't exist...