I was able to test two Utopia headphones and I could not detect any unit variation. And even though I still like my HD800S, I had to sell my HEK V1 after listening to my Utopia for a few weeks. The Utopia is so fast, punchy, with extremely tight bass, clear mids, no problems in the treble area, so detailled and still emotional. Going back to other headphones after some time is so difficult. I never experienced anything like this before. The HEK V1 adds some flavour that I like, but its sound is sooo different from the Utopia, so that I could not go back. The Utopia is so much more technically capable, imho.
Back to the measurements at innerfidelity: Any headphone developer knows that the frequency response differs considerably depending on positioning someone's head. Making different measurements and calculating the arithmetic medium does not solve the problem entirely. So any measurments of the frequency response curve above 3-4 kHz have to be taken with a grain of salt. I like Tyll's assessments a lot as well as his measurements - but people should also keep in mind that companies like Focal, Sennheiser, AKG etc. do have better and more expensive gear available - and even they know about the limitations of measurements!
I also know that channel imbalances can be very annoying, but this problem is rather limited to planars and electrostatics, but not common with expensive dynamic headphones. I once had an LCD-3 with an annoying channel imbalance in a certain frequency area, but never experienced something similar with any dynamic headphone (except Beats - but we are not talking about wannabe headphones here).