In particular, the IS enthusiastic

My impressions:
- Too bad that no ring-type USM was installed. But acceptable.
- The depth of field at full focal length is very low (source surprise!) - 1. Great Bokeh; 2. One should recall that, when you read in reviews about blur.
- Imaging performance and clarity in my view perfectly acceptable.
- The autofocus is ok in Action (eg gulls fighting approach) sometimes a bit slow.
- The image stabilizer: pure enthusiasm. Under ideal conditions, I freehand images with 1/15 sec at 600 mm shot (with teleconverter) without camera shake. Also under real operating conditions convincingly; with the movement of the object I had much to fight over with the camera shake.
- The stabilizer has incidentally two modes: 1. Normal image stabilizer. 2. image stabilization when carrying the camera: pulled the camera in continuous shooting, it is reflected in image stabilization, and therefore prevents the IS works against entrainment.
- The lens has a lock to protect it against accidental retraction.

One star deduction for USM and AF. Nevertheless, all in all a buy recommendation.