Summary: The key reason that I bought this lens instead of the higher quality one of similar range with metal casing is because I'm a traveler. When I'm traveling, my Canon Rebel XTi and between one and three lenses go EVERYWHERE with me. Despite having rather high quality zoom and wide-angle lenses, the one that never gets left home is a nice middle-of-the-road zoom.
Summary: I had to replace my original Canon lens on my EOS T3i which was only a year old. That was a bummer, as the previous lens, (same one) decided to stop auto-focusing just after the 1 year Canon warranty was up. I ordered this one as it is a direct replacement for the one Canon sent in the box with the camera originally. I am very wary that this will also break as they seem fragile in construction and in operation, so I am watching my use with it carefully.
Summary: This lens is fine; it is a basic "stock" lens. It works well for taking portraits and close up shots. However, this seller is lacking. The lens came to me with auto focus not working. This is not a huge deal as the camera does manual focus, but auto focus is a nice feature. The lens also came with no lens cap and in minimal packaging. Beware before you purchase anything from them.
Summary: Purchased this lens as a wider option to the 28-135, knowing it was inferior glass compared to the Ultra Sonic or L Series line. But for the money it is a great option for stills because the image stabilization and auto focus are solid. The wider end of the lens is ok for video but pulling focus on this lens is a pain so it gets 3 stars.
Summary: Its a cheap lens so you can't expect much. I shoot with a rebel t4i and replaced this lens with the sigma 17-70 f/2.8-4 because f/3.5-5.6 is just to slow. I always have to turn up my I so so I can speed up my shutter and that causes noise. Over all its a sharp lens but very slow and when I had it I always wanted it to have a little more zoom.
Summary: Canon gives these lenses away like candy, they seem to come with every rebel on the market currently. The also focus on the lens is shoddy, and even when manually focusing it can be soft. It works well for what it is, but if it hadn't come with my first DSLR I don't think I ever would have bought it as an addition. If you're looking for a nice low millimeter telephoto lens at a low price, this is probably for you.
Summary: Okay. This is the the kit lens that comes with most canon DSLRs. The XSi, 40d and XS already have this. If you didn't buy the camera with this, I'd still suggest you move along. The lens is better than the older version that came with the Rebel XT or XTi, however it suffers from most of the same problems. It is flimsy. The build quality is fairly poor. There is no focus ring for manual, you just twist the end of the telescoping tube.