The autofocus mostly works well and is not overly loud. Especially in low light conditions, however, a manual focus is sometimes necessary, but probably due to the sensor in the camera. For the integrated optical image stabilization provides a relatively good protection against camera shake even in relatively low light. So partly succeed still sharp pictures at a shutter speed of 1/8 second.
Overall it is a good all-round lens whose large focal length range from 18 to 200 mm are purchased with slight weaknesses especially at wide angle. Of course, the quality of the photos does not come close to lenses with a smaller focal length range or even a fixed focal length. However, if you (for example, getting around town) does not take away from space and weight reasons several lenses, but still want to cover a relatively large focal length range, the Canon EF-S 18-200mm IS is a very good choice.