I thought I do a little update regarding my situation with this lens. As you may have read in this thread a few weeks back, I returned a "Ticking" March 2013 copy to GearShop (Amazon) and got a good October 2012 unit and was happy. Well, a few days after I posted, I discovered my lens had a very soft lower left corner from 24mm to about 35mm at f2.8 which indicated a decentered element. This time I decided to return my lens for a refund all together.
Fast forward to a few days ago and I started itching for the 24-70mm II again and found out that I could get it for $1999 via Greentoe.com by naming my own price. Adorama sold it for that price and I had it in my hands in under 24 hours. Upon opening the package, I shuddered at the sight of the "032" serial number. I had hoped that Adorama would ship newer batches by now since some here have gotten April 2013 lenses. And indeed, the zoom ticked while zooming out from 70mm back to 24mm. I was ready to RMA it back to them...
I figured that I test out the lens while I had it in my possession since it was a Friday and any exchange won't occur till Monday anyway. This copy was very sharp...sharper than the prior 2 by a bit at 24mm and slightly so at 70mm. AF was dead on...No micro-adjustments needed. Nice! I had played with it on my 5D3 for an hour or so and I started noticing that I was NOT hearing any noise anymore. Interesting, I thought! So I went into a silent room and zoomed out from 70mm to 24mm. And it was 90% gone! I had to leave for work at that point so I had to put everything away for the day.
I came home tonight and played with the zoom ring immediately after dinner. It was still 90% improved. I can hear it faintly but I needed to put my ear right up to the barrel of the lens and listen in total silence to catch it. My hope is that it will slowly improve to the point where it is undetectable in a week or two. And at this point, I think this is a keeper. 3rd time's the charm it seems. But I will keep an ear out to see if it worsens over time. It honestly doesn't bother me at this point. And reports of later June lenses ticking isn't giving me confidence either.
Sorry for the long post, folks. But I felt I had to share my story with you. I feel I can take the noise off my mind now and simply enjoy photography again. I'm blown away at how wonderful this lens is. I'd just wish it was a tad sharper at 70mm where I tend to use it more for portraits. And I'd also wish it was sharper at MFD. But what matters is that the optics is fantastics and the AF accuracy is super, ultra consistent. I tested the lens with small printed text multiple times and I manually turned the focus ring so it that was OOF from MFD to infinity and it nailed the focus each and every time. That was my biggest complaint when I had the Mark I.
Good luck folks! Please keep us all posted if you had a bad copy.