Conclusion: I can live with all other shortcomings of the lens (distortion, vignetting, lack of sharpness etc) for the sake of the huge 18-200mm zooming range. But, I did some testing, and found that the zooming range is not a true 18-200mm. For example, I set the lens at 200mm, and took pictures focusing at a series of distances (4 ft, 5 ft, 10 ft, 20ft). When focusing 4 ft away, the 200mm focal length was found to be actually only 110mm.
Pros: A great lens to bring along if you only have one, because it offers a nice range of focal lengths. I've brought it on many trips.
Cons: Disappointing quality. I'm fairly active and this lens goes with me on many outdoor activities. I've had to take it in for repair twice, when there has been friction with zoom in/out, and the lens lock functionality failed. I expected better quality from a lens at this price point.
Conclusion: I loved this lens until I used the lock. The lens will extend under its own weight so they provided a lock to hold it. I found this feature after about 6 months when I read the manual. I turned the lock on and it broke immediately. There was a rattle in the lens and soon the lens stuck. This is just what happened to another reviewer. Too bad. I used to love this lens but the lock feature was defective.
Conclusion: I have owned this lens for about 6 months now. The lens is quite heavy so there is a zoom lock to keep the lens from extending. After a few months, this switch didn't work so well and the lens would extend on its own once in a while. Eventually something broke inside the lens and now it doesn't zoom out all the way. I can hear plastic rattling inside the lens. The optics were ok for the price. Definitely not the sharpest.