Summary This is a great lens! I was surprised at how fast it will focus and how sharp the photos are. I only wish I would have purchased it years ago. I have photos that would have been great if they had been taken with this lens. This is my first L lens, but a 70-200 F4 will be on it's way next week. also, I can't say enough good things about ordering from B&H. This was the fifth time I have ordered from them, and I have never had a problem.
If you are looking for a great wide angle zoom, THIS IS IT! A great match for my 20D, and I am sure it will be great for the Canon 5D that is in my near future.
Summary I have bought this lens refurbished at Adorama.
My powerhorse lens, no doubt, on my Canon 20D Camera.
I have used it in:
Thailand, China, Ski tours, the Israeli desert, skiing resorts in Europe, California, Canada, from below freezing to scorching heat.
0 problems. I\d give it a 4, as larger zoom range and IS would make it a 5.
Strengths Weight, overall picture quality.
Price (especially refurbished).
This camera has WAY better build than my sigma 24-70 f/2.8, and picture quality, and AF is MUCH faster on my 20D
Weaknesses Not f/2.8, could use a wider zoom range.
Similar Products Used Sigma 24-70 f/2.8
Customer Service Extremely poor in Israel. Not with product, but with other Canon products.
NEVER visit the dealer, and go with Golden Camera or Erlich.
Strengths Great build quality and nice to use. Good colours.
Weaknesses First, I use it on a Canon 5D, so weaknesses are more obvious than on an APS-C sensor camera. I find it a bit on the soft side, and corners definitely soft at f/8. On the other hand I have not owned a critically sharp wide-angle that goes down to 20mm or less. I previously owned the 16-35/2.8 (first version), and it was also very soft in the corners, but a little sharper in the center.
Similar Products Used Tokina 17/3.5, Canon 20/2.8, Canon 16-35/2.8, Canon 10-22 on 20D
Summary This is my workhorse lens and I love it. It's not as fast as the 16-35 f/2.8 and sometimes I do want the extra f/stop - but the size difference and portability make up the difference in spades. I use this lens every day. It has never failed on me, even in the rain or on the beach (yes, it got hit by a Pacific Ocean curve-ball) and it is about as sharp as it gets. Best professional lens for the money - no doubt!