I purchased this lens to take my baby boy. So far, this is one of the best lens I have seen.
Pros: Very sharp pictures quality. Nice background blurr. The build quality is tough. The manual focus ring is by far the best I have seen. This is an excellent lens for low light.
Cons: This is a really sharp lens but some pictures taken can be blurry. Very challengeing to get clear pictures all of the time. The price is just too expensive for consumer to purchase. Can be very heavy when used for long hike. Slow autofocus, not as fast as my 24-105 is L, but manageable if taken still photo. The range of 85m is very difficult to use in tight spaces, but I knew this when I bought this lens as this is not the lens fault.
Overall, this is a super lens and need to spend a lot of time to play with the focus.