Summary: I'm very happy with the lens for me, an amateur photographer. I had a zoom lens on my old Canon AE1, but I haven't used the AE1 in 15 or more years. I like the idea of an all-in-one lens. I am still learning the ins and outs of DSLR photography and I believe this lens will serve me well for many years.
Summary: No more changing lens. I was looking for something I could take on vacation without changing out the lens everytime I wanted to get a photo at a distance. This fit the bill perfectly. So far I have no complaints at all about this lens. The pricing was very fair, compared to a similar lens that Canon has available.
Summary: This past October I attended my sister's funeral in Canada and one of the attendees had a Sigma 18-250mm lens attached to her Canon T3i. After swapping cameras with her for while I fell instantly in love with it. I owned the T4i along with a Cannon 75-300mm, and a 18-55mm lenses. I needed an in-between lens so that I would not make quik swaps between the 75-300 and my 18-55, and end up missing something.
Summary: I have been using this lens for about a month now. The build quality is very good. This replaced both my NIkon 18-55mm kit lens and my Sigma 70-300mm lens. This lens has an effective optical stabilization which was a real plus for me. The body is surprisingly short for such a high zoom lens. The focus is internal and super fast and quiet. I love to shoot pictures of almost anything and this has become my permanent lens.