Summary: I made a comparison between this and the 70-200 F2.8 non IS, as they were around the same price. I was expecting the heavyweight F2.8 to be better; but if anything, the F4 was sharper and the IS a real bonus. Lightweight and highly portable; its a great travel lens. Bokeh is good for an F4 Image quality is superb wide open and gives good results with a 1.4 x extender. Given the price of this lens; having to pay extra for the tripod mount is a big black mark for Canon.
Summary: I've owned another copy of this lens before and before that I rented it a couple of times. I found it to be the best zoom Canon ever produced. This copy that I recently bought from Walmart.com however, seemed to back-focus a lil bit. My camera doesn't have AF microadjustment and I didn't want to send all my cameras and lenses to Canon to caliberate so I returned this lens and I'm going to order a replacement soon.
Summary: Very good lens for outdoor shooting in bright light. Lightweight and durable. Fast focusing and produces extremely sharp pictures when light is sufficient. For F4.0 lens having image stabilization is very important. Very versatile lens. I would recommend it to anyone who needs to get closer to the action.
Pros: Consistent Output, Durable, Easily Interchangeable, Fast / accurate auto-focus, Lightweight, Rugged, Strong Construction
Summary: I use this with a 5D and the combination creates some lovely photos. I had to try two copies of the lens because of corner softness. Its capable of producing gorgeous shots. Works well with the 1.4x adapter.
Summary: I teach photography at a large university and work as a portraitist. My favorite portrait lens is the Canon 85mm f1.2L, but occasionally I have need for a longer telephoto, so I bought this 70-200mm f4L IS. I honestly did not have high expectations for it, since it is about half the price of most of my favorite lenses. I had previously owned a Nikon 70-200mm f2.8 VR lens, and was not impressed with the image quality or the "vibration reduction" technology.
Pros: Durable, Lightweight, Quick Focus, Rugged, Sharp Focus, Strong Construction