Disappointed

vignetting:
i always shoot in raw and use photoshop cs6 for post. So correcting the vignetting, CA or distortion is not a problem however i find the canon ef-s 18-200 IS suffers from major vignetting on the longer focal end 100-200mm especially when decreasing fstop from f/11-f/22.

AF:
i tested all 9 points individually and all 9 together got the same results also it doesn't matter what ISO, f-stop or shutter speed i use, it could be hot sun outside using ISO 100, f/8, 1/640 when zoomed in to 80mm and upwards, 80%-90% of the times the lens hunt trying to acquire a focus point on the subject.
I don't even bother try anymore in poorly lit conditions because anywhere that requires me to use at least ISO 800 with that lens its a 100% guarantee than from 80mm and upwards, i would never get a focus lock on subject and from 18-70mm is a hit and miss (sometimes it locks no problem sometimes is doesn't)

I know vignetting, CA, distortion, zoom creep are all things super zoom lens suffer from but my major problem is the AF. It just totally sucks and i cant count the numerous times i missed 'that special moment' because of the lens forever hunting trying focus. Sometimes i had to resort to manual focus.
Could just be the model i have was from a bad batch - never know.
One thing i notice that i forgot to mention also is that with the recommended lens hood attached, the ends of it are visible in my frame when zoomed out at 18mm and disappears from the frame by 24mm.
Anyways i more use this lens for landscape now because its a total let down for me as a walk around lens

Tested on t3i and 60d