Summary: I believe I got mine in 2006 or 2007 and it has never disappointed. The f4 works for most outdoor use and it is a lens you can carry easily compared to the 2.8 with foot. The amazing quality really showed when I used it with my now retired film body, but also shows when my 17-85 is at telephoto and this as at its widest.
Pros: Amazing image quality and image stabilization.
Cons: No weaknesses. Nicking it on price would not be fair because the big white Canon lenses are top tier and it seems like they spare nothing to make them.
Excerpt: I hope to use this lens for creative water/waterfall or water in motion shots with an ND Variable filter. I had a f/2.8 of the same style but down sized because I feel this one will do almost as much and I have money left over. It is light weight and fast. Slightly noisy motor, that I hope isn't an issue in the future. The size is perfect, too bad it doesn't come in a f/2.8 at the same size.
Pros: Easily Interchangeable, Fast / accurate auto-focus, Lightweight
Excerpt: After months of research, I purchased my first L series lens, the Canon 70-200f/4L IS USM. This lens has incredible, fast autofocus and produces super sharp, crisp photo's. At half the weight of the f .8 and hundreds of dollars more in my pocket, I can't see how anyone would go wrong with this lens.
Summary: Image is excellent at all focals starting from f4. Close up image (at MFD) is very good, except at 135-200mm on my copy. For this situation I use only 70-100mm. The slipping focus is history now after free service.
Pros: excelent IQ, light weight, very good IS and finally but not the last excellent IQ :)))
Cons: the hood could be better, slipping focus but after service it's ok
Excerpt: I use this almost as a everyday lens. Primarily for wildlife and animals around the house and some minor league baseball games. Works great as long as you have ample light given it is an f/4. Although it can get some great shots of the moon.There is a slight mechanical whir when you autofocus, it worried me at first but after looking into it there is nothing wrong it is a normal thing for the lens to do.
Pros: Consistent Output, Easily Interchangeable, Fast / accurate auto-focus, Lightweight, Nice Bokeh, Rugged, Strong Construction
Excerpt: Is versatile for closeups as well as distance photos. I used it to take a closeup of a blossom just across a small creek that I couldn't wade through and the lens produced a great close up shot with deep color, clarity, and just right blur in the background. Am using the EF 1.4 extender for distance shots and that works great as well. I was considering the L70-300 too, but all indications were that the L20-200 f/4 was a better choice.
Pros: Consistent Output, Durable, Easily Interchangeable, Fast / accurate auto-focus, Lightweight, Nice Bokeh, Strong Construction
Summary: Read all the reviews before committing to buy and was not disappointed, the IS all canon claim and the IQ beyond reproach. WOW this is one great lens..... to me well worth the premium over the older non IS version. Used with a 5d mk111 and f4 no real handicap even when used for sport/ low light.