As others have mentioned the lens is quite solid but the hood is cheap feeling.  I got this for my D5100 to try to get some decent indoor volleyball pictures.  I wanted a fast lens with a little magnification for for action at about 10-30 meters range.  This lens does just what I wanted.  The magnification factor for an APS-c sensor  about right. If there are any distortions in the corners I won't notice them on my camera.  I don't think this lens is recommended for a full frame camera.The manual focus is smooth and doesn't pull.  I am still not sure this is the best lens for what I want since the DOF is only about a foot or two at 30 feet and f1.4.  That is just physics and nothing wrong with the lens itselfI plan on doing some portrait work with it in the near future and expect good things. 

Question: Is the focus ring smooth?
Answer: The manual focus is smooth