I am still new to both the equipment and photography - two points
a. if you are going to take videos then its worth it - because you can freeze an image and potentially blow it up - I am sure it wont be as clear as a using the very expensive lenses.
b. if you are looking for super sharp images then its going to frustrate you a lot - to that end I am renting the 200 - 400mm prime lens to see the major difference to compare it to the 100 - 400mm and teleconverter. I wish I could upload pictures and videos