I had the kit lens for only one day, but above all the intensity was a little tight, I often need to photograph in lower light. Thus I have given away there. In addition to some existing prime lenses I searched then but a useful but low-priced zoom lens because it is sometimes but comfortable.
For me, the biggest selling point compared to the kit lens are consistently getting slightly better light intensity, which ultimately also ensures better focusing performance. Where it was just with the kit, the Sigma is still felt confident during AF.
The second major advantage is the mechanical design. Internal focusing, unchanged overall length when zooming, nothing turns and pushes outward. In addition, Focus and Zoom have a pleasant rotational resistance, no noticeable tolerances. That's all much more pleasant than in the kit.
In addition, it is larger in diameter and looks better. Not that that would be the most important when taking photographs, but with this lens one looks a bit more professional than ever before with the kit for the average person. For me personally, but especially the haptic profit is very pleasant.
Also very positive, I find the very good working OS. I testhalber even photos with 1/4 sec. can make out of his hand, which made me a bit impressed added.
For imaging performance. Here, opinions are so apart. I would like to summarize it that way. One can find situations in which the Canon will be better, as there are situations where the Sigma has the edge. I personally am very satisfied and could feel the Sigma more good (and correctly focused) making pictures - that is what matters at the end yes.
On the subject of video: also on the 650D you can not shoot with AF with this lens. In normal shooting the noise of the focus motor never fails to actually. In Videoaunahmen it will at least then it added greatly from the internal microphone. Furthermore, the AF triftt also rather rare in video mode. Since it takes probably but a STM lens from Canon. Unfortunately could not test yet none. But I've filmed with manual focus already very nice material. As I said can be turned very pleasant the focus ring. By the way no manual intervention in the focus in AF mode possible, in other words, the ring rotates with the automatic focusing. When films (or generally during manual focusing) I find these "fixed link" naturally good. So for me, more of a benefit, since it suits the way I work.
Something else that I want to mention in passing: I have used the lens out of curiosity to an analog full-frame Canon. This accepts the lens without a murmur. Of course there are strong vignetting at short focal lengths. I found very sympathetic, and you can make time.
Conclusion: in terms of the price I forgive 5 Stars. As an alternative to Canon 18-55 kit it has advantages in terms of feel and the light intensity. The image quality is equal on average. Buy should it, who likes to have a little more in hand, often snaps at scarce lighting conditions and its kit lens is good going on or even none at all has. Because then the charge is so low that it is worthwhile in any case.