@ Krob78: bad luck, you have got a bad copy.
I had a hard time even thinking about buying a third party lens, after using almost 30 years only Canon.
The drive is louder, but extra sound like you described seems to be a serious damage.
I have read many reviews on the net before buying, Tokina seems to have issues with quality control.
So I choosed to order it from a place, where I can send it back with no problems.
I wish you good luck with the replacement.
Thanks Alex, I did send it back however I decided not to opt for a replacement. Although it was mostly good, the weight was really absurd and I decided I didn't want to "try" another one, so I ended up with another Canon L lens... I picked up a 17-40mm L and it works great, just like I knew it would. Surprisingly and conversely, the 17-40mm L is amazingly light!! Almost too light for my liking!!
But no flare issues, nice color rendering, sharp. Price was excellent at only $625 for brand new in box. I use it mostly for interior Real Estate work, so f/4 isn't an issue as I'm shooting it primarily indoors at f/5.6 and f/8. A little wider would have been nice but the lens will pay for itself very quickly with a couple of shoots.
I wanted the 16-35mm f/2.8 but decided with rumors of a new wide angle being announced later this year (hopefully with IS), I decided to pocket the almost $800 difference and I'll take a look at the new offering when it comes out... If it doesn't surface, I'll think about upgrading at that time. For now, other than the amazing lightness (feels cheap), of the 17-40mm, I'm set...