First, let me say this is a superb lens: its sharp as a tack, autofocuses fairly well and pulls off the difficult twosome of being both reasonably sized and sturdily built. But it reminds me of the expression “A triumph of technology over common sense”. It does what it does very well, but I personally don’t need what it does very often. If I want a telephoto lens, I generally want at least 400mm, and with a teleconverter mounted the 100-300 loses some of its luster and becomes a rather ordinary f/5.6 lens. If I’m shooting up to 200mm, I’d rather have an f/2.8 lens. So I find it useful as a telezoom on a crop camera, or to get a bit more reach than a 70-200 when the light is good. When I use it, I really like it, I just don’t use it that often.