As you unpack the first shock ": The thing weighs over 600g, but this is exactly why I this lens personally find so awesome by the weight, it is possible the camera with the lens much quieter to hold in your hand than with lightweights.." , Furthermore, immediately noticed the very good workmanship. Nothing wobbles or rattles. No Game. Everything can be very soft and move without jerking. A Lock function at 70mm prevents unintentional "move the lens barrel. The metal bayonet completes the very good workmanship.
Some say the aperture value is not indeed the best. This may be. But by the extremely well-functioning IS (Image Stabilizer), it is also possible to make hand-held shooting at a shutter speed of 1/60 sec, without recognizing a loss of sharpness. Thus one makes the poorer aperture value up for it. The IS is the 3rd generation and ownership 2 modes. A mode compensates for both horizontal and vertical movement. The 2nd mode compensates only horizontal movements. Ideal for Mitsch Wenken a moving object (eg a car) on a tripod. The Ultrasonic Motor (USM) is as always very quiet and very precise. Even hand-held shooting and a focal length of 300mm (480mm so at APS-C sensors) super crisp images are possible. The picture quality is top. With my camera to detect any vignetting and no distortion. This could be eliminated but through various programs (including the Canon Professional Program). The colors and the contrast is just tired.
In various forums, this lens is advertised as a hidden L lens ". It iss also. I could 70-300 4-5,6 direct comparison with the 70-200 4 L without IS. The image quality was not much better here . The 100mm longer focal length, the 50 euros less, and of course by the IS much the decision on the 70-300mm.
One shortcoming there for this lens already. The IS works well, but is clearly heard. For me, this is of no interest. The camera makes when you press the shutter button louder sounds ;-)
I'd make up my mind at any time for this lens. Here the price-performance ratio. Who can do without more focal length to 100mm and too much "has money, should the 20-200mm 4 L IS USM buy for more than twice.