First step has only ever activated when starting from a near stop, so either when you're starting moving for the first time, or when you've gotten slowed down to the point where you're near stopped. (It can only activate when you've got < 1.5 acceleration "units" of velocity, no matter where you are on the field.)
It's always been far less useful for RB's than WR's for instance, because of that fact. The RB is usually up to speed when he hits the hole, so first step wouldn't even have a chance to do anything. Quick cut is more useful, I'd say, for moving quickly through the line.
It can help greatly if you have to make a big cut, I guess, because you have to slow down a lot.
Actually, now that I think about it, making them slow down might actually INCREASE the value of first step. If they have to slow way down to break through the line, they will be more likely to be in a position to use it after they do.
