I had two versions of the non-L 70-300 (I + III) and I never got happy with them. The pics were not too bad but not too good either (lack of contrast and sharpness). But where the non-L version really do not deliver is build quality: the barrel is made of plastic and not weather/dust sealed at all. There is a considerable amount of lens creep to deal with too. The L-version on the other hand is extremely well built and has a zoom lock. I never regretted shelling out the money for this lens .