The blue square flickers on my old 20" Cinema Display. It's flicker free on my MBP and iMac 24. Everything else is fine.
My issue with all of this is -- Why? I'm fine with the 20" display and never would have known there was an issue. Why would I even look for these problems if I'm happy with my Mac. Unless the problem is very obvious I don't see actively looking for problems.
Maybe, I'm not that picky when it comes to displays. I've never (or known I) had a bad one.
Cheers,