My favorite lens, which has been in my possession for 3 years now.
+ Performs very good optically already with maximum aperture, but the focus will be even better if you mix down a little.
+ Very fine so-called Bokeh (softness / appearance of the blurred areas of the image).
+ Very nice build quality.
+ Good feeling in the focus ring.
+ Good backlight features (But it is saving by Canon to not send with a lens hood, because it may be needed in strong backlight. It may not cost much money in manufacturing. Therefore, I do not put a dollar in the ratings).
+ Quiet and precise autofocusing.
+ Internal focusing. (Nothing that moves on the outside. A big plus when shooting timid insects).
+ Relatively long working distance at 1: 1 scale (about 15 cm from the lens)
+ The sharpness is very good at all distances, not only within the "macro-region".
- + Image stabilization (IS) would be fine in some situations but absence makes the lens affordable in price which is good.
- As mentioned above - a lens hood Canon could almost sent with.