Considering Tokina 11-16mm but worried about soft copies

Hi everyone!

If there's one thing I learned from using a 18-55mm IS kit lens on my 60D, it's that I was always hoping for a wider angle, and so it only made sense for me to go in that direction.

I've been doing a ton of research and it seems that the Tokina 11-16mm is highly regarded on these forums, and is often recommended over the Canon 10-22mm.

I also considered the Sigma 10-20mm (both versions) but I'm told that unless I am on a budget, the Tokina should be the better lens for me overall.

I want to get the lens, and I will get a Mack international diamond warranty for it.

My main concern is that I have very little experience with the lens or other UWA lenses and I'm worried that I wouldn't quite be able to realize if I was getting an imperfect lens.

Are bad copies so terrible that even amateur like myself could easily tell them apart?
Thanks for your insight everyone!