It is definitely worth it. You get a 35% bonus on every skill you have.
Thunder bolt goes from 60-81 atk
cold beam goes from 100-135 atk
fire arrow goes from 120-162 atk
ice strike goes from 90-121.5 atk
explosion goes from 120-162 atk
shining ray goes from 105-141.75 atk
AND the 4th job attacks go from 570 to like 770 atk.
Do you see my point?