Then, that's not turn-by-turn. It's just the old style directions that are in every previous iOS
The old style does not update automatically based on gps position, it requires you to press the next arrow yourself. iOS6 will change it to where it will change the onscreen direction to the next one you need automatically based on your gps location, so that is turn by turn directions.
On my vehicle navigation I run without sound on my turn by turn, so the iP4 will perform very similar to it. To me, the constant "turn right ahead" is annoying as h3ll.