Excellent stone! 1 1

The Canon 70-200 IS is a fabulous goal!
Solid construction, pleasant to use, quiet and fast AF, and especially its sharpness is remarkable. It produces high contrast pictures and fine details. In addition, it generates pictures with beautiful blurred bokeh very valuable portrait.
With the SI useless to work on a tripod, despite its 760 g in addition to those of the device ..., stabilization compensates perfectly possible shake. According to Canon, it saves up to 4 speeds.
Its optical glass UD and fluorite lens is of high quality and guarantee an effective correction of chromatic aberrations.
Distortion and vignetting are also very well controlled.
So, admittedly, it opens "to" f / 4 but now I would say that unless you absolutely need an aperture of f / 2.8, f / 4 release is more than enough because its performance is already excellent. This objective is also a more objective pro amateur.
Note that this lens is used with EF extenders x1.4 and x2 but with the x2, you lose a priori FA.
Personally, I use coupled with a 7D and 40D previously a.
In short, in the end I would say this is a lens that you can not be disappointed!