It's a good lens, but not an $850 lens. The lens has a nice build quality while remaining light weight, a constant f/4 aperture, narrow zoom range and is not particularly sharp.

  Build: 7/10                    - Light, but it feels good, no loose parts.
  Handling: 7/10              - Zoom action is smooth, although it increases in length as the focal length is decreased. Focus is fly by the wire.
  Performance: 6/10       - Not the performance you'd expect for a lens that came out at $900.
  Value: 4/10                    - Overpriced.
  Overall: 7/10                - Decent, but not great performance in a small package.

Practicality for kayaking: 9/10  - It's small and light for what it is. If this lens was $400-500 I'd recommend it. Perhaps I just got a bad copy, but as it is, it's just too expensive for the performance it delivers. Even at f/8 the lens just never has any bite.