No, just location to location, enemy to enemy. There's almost no need for exploration except for looking for the enemy computers or whatever for achievements. On rails isn't a bad thing, people are just homos. And Kosma is wrong. First time I played MW2, on the snow level, I futzed up and they (the guards patrolling in the trucks were alerted because I got cocky). Second time, I managed to get past the entire guard without being caught. So no, it's not an open ended fps, but it gives enough opportunity to change things up the next time you play, with a variety of ways to do them.
And this is ignoring that the world "on rails" is being misused. A TRUE on rails game doesn't let you go back. You can only go forward, left, or right to strafe and hit enemies/enemy projectiles. A game like MW2, which allows the play absolute freedom, and ability to go back is not an on rails game.