I don't think this poll is very useful.
First of all, the original thread of the clicking zoom at http://www.canonrumors.com/forum/index.php?topic=15231.0
was made back in June 2013. That was 9 months ago. Many of the people who reported that they had a problem on that 15 page (!!!) thread are probably not going to report on this poll just b/c it comes so late.
Second and more importantly, most people who get a clicking or defective lens exchange it back to the store over and over again until they get a non-defective one. There are many people who have exchanged at least once, and there are even stories in these threads of people exchanging 5-8 times until they got a good copy. Yet if they came to this poll, they would have to select the "no problem" option, because that's what they have now. The poll would not capture the fact that they sent back multiple bad copies.
The poll question of "Do you have a problem" is therefore useless. More useful would be "Have you ever received a copy that had a problem", but even this question would be inadequate because it would not accurately represent somebody who exchanged 5 lenses until they got a good one. So the most useful poll question would be "If you bought a 24-70mm 2.8L II, how many defective copies have you received and exchanged/returned", with options 0 [received good copy first time], 1, 2, 3, 4, 5, 6, 7+.