I got a chance to demo these at the Ableton Loop conference a couple of months ago... they had a Nura room set up with a bunch of headsets hooked up (via Bluetooth) to iPhones, and some salespeople there to explain the tech, assist with the measurement process (which is actually ridiculously easy and takes less than a minute) and answer questions.
Yes, the measurement process is based on otoacoustic emissions, which is the same technology they use to do hearing tests on babies, who can't tell you what they're hearing (or not hearing). So it's grounded in solid science, you can look it up (or follow the link a few posts back).
The sound, once measurement was done, was quite extraordinary. Rich, full, detailed, gorgeous sound from everything I listened to on them - and I checked out a number of things I know really well including some Pink Floyd and a few of my own mixes, which I was able to access since the iPhones were running Tidal. I was *extremely* impressed. I literally didn't want to stop listening to them.
The product also seems remarkably solid in terms of comfort, design and manufacturing quality, especially for a 1.0 product from a brand new company. They've got a lot of things very right with them, which helps justify the relatively high cost - though they're not ridiculous compared to anything that can reasonably be considered competition.
If you read a few reviews you'll probably hear similar reports, and you may also hear my one misgiving about the whole experience - which is that if you turn the personal processing off, to hear the 'vanilla' sound of the phones, they sound remarkably bad - like, every bit as bad as the processed sound is good. Since this functionality - turning the processing off - is always there, despite the fact that if you heard the sound without you would honestly never, ever want to hear anything that way again, it's extremely tempting to conclude that they've deliberately made it sound crappy to help market them in test settings like the one I was in - which seems to be the main way they are marketing the product. If so, it's smart, but seems a bit sneaky.
On the other hand they also let you try out the profiles of the last few people who've done the test, so you can also hear what the system would be playing for them - and that just sounded WEIRD - not bad in the same way that the 'vanilla' sound was bad, but distinctly *off* - which does tend to support the theory that yes, hearing really is that individual.
And who knows, *maybe* something about the technology requires that the unprocessed sound be like that, I don't know, but it just struck me as odd, since the next day for reference I went and demo'd a pair of high-end Bose noise-cancelling phones, which of course are designed to sound good to everybody and aren't performing any individual testing/processing magic, and they also sounded great to me - as, of course, do my old standby Beyer 990's here in the studio. So it's a bit mystifying.
Anyway, I encourage anyone to give the Nuras a test drive if you find yourself with the opportunity. I didn't end up buying them (yet) as I'm not swimming in money at the moment, but I was genuinely impressed and the 20% off coupon they gave me for doing the test was seriously tempting. It says it expires within 10 days, but I haven't tested this.