Close to perfection 1

To:
+ Precision and comfort of the manual focus ring (lauto Focus is also excellent (fast and accurate), just that it is less conventionally used in macro)
+ Hybrid stabilizer (it was discussed and ballast perhaps, but for me SI brings a real plus (I must admit I do not always carry around a tripod))
+ Build quality (standout in the L Series)
+ Optical quality: correction software have nothing to rectify the side of particular distortion
+ Quality of the bokeh (it joined some optical quality point). In this regard, some people advance the idea that the bokeh is even better with a full frame but we go there in the considerations which I am not able to realize in practice "current" ...

=> Excellent goal

Chicanery ...
~ Sun visor is impressive: hard to carry around the device when it is mounted on. And when you go back to the goal, the focus is no longer available
~ JOperation very little focus limiters (or ranks dauto focus), respectively: 0.5 - infinity and 0.3 to 0.5

NB / I am the User with a 40D (aps-c with conversion coefficient of 1.6) and a 5DII (full frame). And more often freehand: a real pleasure!