Canon EF 100-400mm f/4.5-5.6 IS USM Lens

I've been using this lens almost daily for nearly 2 months now and I am liking it very much. I was a bit put off at first by the push-pull zoom until I discovered its great benefit for those times where you need a quick offhand shot in conditions where auto-focus does not work reliably and the subject is moving to and fro. In this case, the lens can be zoomed and focused at once by moving the zoom barrel in or out as the focus ring is adjusted. With a bit of practice, this can increase the utility of this lens considerably for lower light conditions, especially when used in conjunction with the dual mode image stabilization. I've also noted that the image stabilization (mode 1) works well with a tripod if a bit of flex is induced once stabilization is activated (by pressing the shutter button half-way). It works like this... lens and camera are tripod mounted, lens is switched to manual focus mode and mode 1 stabilization, shutter button is depressed half way to activate stabilization, very slight flex is induced into the system by light/slow movement at the camera... up - down - left - right and shoot as you relax flexing. This for me works well, allowing stabilization of slight vibrations without resorting to mirror lockup. While delicate persons may struggle under the 48 oz weight, I find the heft of this lens to be a plus when offhand shooting at the higher magnification ranges because of the damping effect of the extra mass enabling image stabilization to work more effectively. This lens is rugged and of good optical quality. While the lens may not be right for high speed action shots in lower light conditions, it is a great general purpose telephoto zoom nonetheless, and I am very much pleased with its overall performance.