Extracto: When shooting with my new lens mounted to my 5D, the images I tried shooting (Macro, flowers) just didn't seem as sharp as those I came across when deciding on the purchase. And even after comparing the lens with a friends shot of like images, the images my new lens shot just seemed a bit softer. I was told on forums that sometimes this happens. Not sure what to do about it. I actually wish I hadn't sold my non "L" 100mm macro now.
Extracto: The focus ring turns only about 135 degrees from infinity to max close focus, so the manual focusing is very touchy especially at high magnification. There is an element in the lens that rattles and can visibly be seen moving around when the lens is not on the camera. This stops when the lens is attached. I'm told this is normal. It seems that there is potential for damage during transport.
Extracto: This lens is 5 stars for sharpness, quality, and versatility. My only complain is that my copy had focusing issues right from the start. Luckily Canon, is great at getting it fixed ASAP! The warranty is great with Canon. I also know when they fix the focus algorithm issue I will have my copy of the lens back which is insanely sharp.
A favor: Consistent Output, Durable, Strong Construction
Extracto: Optical properties of this lens are excellent for macro and portrait work. Autofocus is good. However, the lens disappoints when focusing manually. The focusing threads are crude making it very difficult to find a sharp focus for macro shots (where manual focus is needed). Finer threads would allow for a more critical focus adjustment. Also, the focus ring is "loose". I.e., the slightest accidental touch will disturb the focus setting.
Extracto: This is a nice piece of glass , but I am terribly disappointed in the manual focus. It is a rough adjustment, where what is needed is a fine adjustment. Also it is easily disturbed - throwing the image out of focus with the smallest accidental touch of the focus ring. How much would it increase the cost to use a finer thread on the focusing ring?
A favor: Fast / accurate auto-focus, Lightweight, Nice Bokeh