Summary: I bought this lens primarily for low light use since I like to shoot at night. So far so good. I have not critically tested the sharpness but casual observation indicate good resolution although not as good as the Nikon lenses. Mechanically it works great. I like the focus lock and its convenient location. This is good for shooting in low light. Lastly, it is a good value for the money.If you get a comparable lens expect to pay at least $100 more.
Pros: Consistent Output, Durable, Easily Interchangeable, Fast / accurate auto-focus, Lightweight, Strong Construction
Summary: I'd rather give this 4.5 stars than just 4. Autofocus is fast, the lens is sharp, the close-focus marco ability is great. Overall, this is an extremely versatile piece of glass. If this lens had a constant 2.8 aperture (and maybe image stabilization) this would be perfect and it would never leave my camera.
Summary: As an owner of a Canon Rebel Xti its kits lens became rapidly a disappointment because of the soft images it produces. I made some research on various Websites comparing some lenses (for example: Canons 18-125, Sigmas 18-50 EX) Finnaly I decided on this one for its aperture range, sharpness, zoom range, quality, and price. I tested this lense during the holidays and it's standing to its reputation.
Summary: I bought this lens to replace the 18-55mm lens that came with my Canon Rebel Xti. I wanted a faster lens with more zoom range. This lens fits the bill. I sold my 18-55mm lens and use this lens for my everyday walk around lens. This is the first non-Canon lens that I have bought and I'm very happy with it. It is heavier but feels solid and more professional. A great upgrade and much more cost effective than the other options!