I had two of these lenses and both were crap.
Thanks for contributing with your experience. Your review strikes me as a bit too emotional, exaggerating and contradicting with other reviews for me to take it seriously, in particular since this also is your first post and we haven't had a chance to gauge your experience, skills, language and general attitudes. I cannot say I've seen internet flooded with negative reviews of the lens. To measure barrel distortion you need to carefully align your paper wall with the sensor plane - they have to be absolutely parallel. This doesn't seem to be the case in your example photo, which looks as if tilted slightly downwards. Distortion has previously been measured to be very low, ~1% barrel at 24mm and 0.02% pincusion at 70mm, uniform across the frame
. Very few issues with flare and ghosting, even when shooting into the light. Vignetting sure is a problem at f/2.8, but by f/5.6 it's down to half a stop in the corners, and is noticably better than Canon's current offering.
Good luck with your purchase of this lens....
Thanks, I probably will get it at some point, and then I will take care to evaluate the lens to check for any problems you mentioned. Maybe Tamron has problem with its QC, but at this point I cannot exclude user error.