Bests & Worsts Reviews from Amazon

I have owned this lens since February 2005 and have used it exclusively with a Canon 20D. This is the second L-series lens I've bought from Canon (the other being the 24-70mm f/2.8L). Before buying, I researched the different versions of this lens Canon offers (IS, non-IS and non-IS f/4). I looked for every reason 'not' to spend the money on the IS version but ultimately got it anyway. I have never regretted the purchase. You should know that IS (Image Stabilization) is not a miracle cure for camera shake, but it does give you the equivalent of two or three stops in terms of usable shutter speeds. A motorized gyro inside the lens helps compensate for a modest amount of camera shake. It's powered by the camera's battery. That means if the slowest shutter speed you can shoot handheld without unacceptable blurring is 1/60, you will be able to shoot 1/40 or maybe 1/30 with IS. In some situations, that's the difference between a photo that's a keeper and one you toss. Of course, you can still take blurry photos with IS--as I said, it's not a miracle cure, but there's no question it's a worthwhile feature. This version of Canon's IS can be used with a tripod unlike the older version on some other Canon lenses such as the 100-400mm L, which cannot. It has two modes, one corrects for vertical motion only (for shots where you pan with a moving subject) and another that corrects for both horizontal and vertical motion. Note: IS does NOT compensate for subject motion--the only way to slow subject motion is with a faster shutter speed. IS is purely a feature that helps avoid the blurring caused by the camera moving. My copy of this lens is very sharp at all focal lengths. Color and contrast are excellent. I really don't have a single complaint about this lens. Some people find the weight objectionable, but it hasn't been an major issue for me. Unless you need to be physically running around to capture your images, or unless you have to hold the lens to your eye for lengthy periods (isn't that what tripods are for?), I don't see that it would be a problem for most average-sized, healthy adults. I often carry my 20D in a shoulder case with this lens, the 24-70mm L and a 580EX Speedlite. Hours of carrying this bag around does require transferring the load from shoulder to shoulder periodically, but it's a price I'm willing to pay to get quality photos. I own Canon's EF 1.4X II teleconverter and have used it on this lens with great results. The 70-200mm is so sharp to begin with that there's no appreciable loss in sharpness when combined with the 1.4X TC. Reportedly, the results from the 2X TC are not as good, and some find the falloff in sharpness to be too much (not just with this lens, but with any of the telephoto lenses). This lens is highly recommended. If you can get over the steep entry price, you'll have a high-quality optic built to last for years to come. Of course the non-IS versions can take beautiful photos as well, but having lived with IS now, I've been spoiled. Update 5-17-10: It's been 4 1/2 years since I wrote this review, and I continue to use and enjoy my 70-200mm, which is now paired with a Canon 7D. Anyone considering buying this lens today, however, should know that Canon updated this lens earlier this year. The mark II version has improved optics and the latest generation of IS, but it is priced $500 (MSRP) more than its predecessor. Check Amazon's listing for the mark II to see the exact difference in price.