Excerpt: Lens is sharper at f5.6 than f4. Some images are very sharp, others are not at all. I am in the early stages of using the lens. Further testing is needed, but am concerned about the occasional blown focus.
Pros: Durable, Nice Bokeh, Rugged, Strong Construction
Excerpt: I looked into pages and pages of reviews before buying this lens. Of course I wanted the 2.8IS but I couldn't afford or rationalize paying for it when I could just rent it for the shoots that I needed it for (infrequent). I recently shot a beach wedding with the F4IS on my 7D (my backup) and I was really impressed with the sharpness at F4 and it's overall performance focusing in AI Servo.
Pros: Consistent Output, Durable, Easily Interchangeable, Fast / accurate auto-focus, Lightweight, Nice Bokeh
Summary: This is THE go-to lens for anyone on ANY size sensor, 1.6x, 1.3 or full frame. Images are tack sharp and its MTF charts are bested only by lenses that cost several thousand dollars. The stabilizer is good for 4 stops and works great for pans. I sue mine on a 60d and 5d, on the 60d it works out to a 120-320 f4 and gives me a little more reach, but on the 5D it's a fantastic portrait lens. The range is almost walkaround perfect and the lens feels great in your hands.
Excerpt: This is a great lens, no doubt about it. The f2.8 however, is better. BUT - it's much heavier, and much more expensive. So, for the money (in comparison to the f2.8), it is a very good compromise. You may lose 10% of the ability, for 70% bnefit in costs and weight. In my head, that's worthwhile.
Pros: Consistent Output, Durable, Easily Interchangeable, Fast / accurate auto-focus, Lightweight
Conclusion: Absolutely an unbelievable lens. My previous Canon 70-200 was the f4 non-stablized - I liked it but didn't use it often because it needed a high shutter speed (at least 1/250) and the results weren't quite as sharp as I had hoped (date coded as 2005). Eight months ago I upgraded to the stablized version (date coded as 2011) and I fell in love with this lens. A much, much sharper image combined with the stabilization allows a shutter speed as low as 1/15 of a second.
Pros: Fast auto-focus, Superior build quality, Super-sharp images, light weight
Excerpt: I use this lens in a variety of situations, from event photograpy to wild life photos. I considered both the f/2.8 and the f4.0. For me the decision was quite simple, money aside, both lenses have great reviews. So, since I spend a large amount of my time lugging lenses around the Mountains of Colorado, weight became the deciding factor for me. I have used both the f2.8 and the f4.0 versions. I can assure you I am not one bit disappointed in this lens.
Pros: Consistent Output, Durable, Easily Interchangeable, Fast / accurate auto-focus, Lightweight, Nice Bokeh, Rugged, Strong Construction