I had the version I and later also have Canon 100-400, Sony 70-400G. The version I was the least satisfied one....and this one showed huge improvement in handling thanks to AFS, sharpness.
It was very difficult to accept the product initially because of increase in price to 2.5 times of older version, and also being more expensive than sharper competitors Sony 70-400G and Canon 100-400L. However, as a stand alone product, the convenience and image quality remained unchallenged. For starter wildlife shooter, this is a highly recommended one except if you take prime telephoto lenses into account.
It was very difficult to accept the product initially because of increase in price to 2.5 times of older version, and also being more expensive than sharper competitors Sony 70-400G and Canon 100-400L. However, as a stand alone product, the convenience and image quality remained unchallenged. For starter wildlife shooter, this is a highly recommended one except if you take prime telephoto lenses into account.