Sounds intriguing. Have you heard the V-Moda M-80? Thanks for the review.

Sorry, no V-moda! They don't sell them anywhere around here :/

I just got my kef m500 yesterday and right out of box the highs were very harsh for me... I had similar experience with ultrasone pro 750 which I sold but it seems like I am the only one who think of it this way... Maybe it requires burn in for it to smooth out? or maybe I am just too sensitive with the edgy highs? My other headphones were ATH ES10, DT880 pro, T50rp, ATH ESW9, M50, and dt 770 pro. out of all I thought ath es10 was the best but I guess I should wait and see how m500 compare after its burned in.

I've found the M500 to smooth out slightly with burn-in, but even out of the box they certainly aren't harsh the way Ultrasones are. If you find them very harsh, maybe your source components or source material is to blame??

The certainly have smoother treble to my ears than the M50, much smoother...

Fantastic review, but what did you play the music from for your impressions of the M500? Smartphone, laptop, etc?

I mostly use the M500 with the Meridian Explorer DAC connected to either a macbook or an iMac. 

 Okay. Have you tried it without the DAC? I'm curious as to if it still sounds good without an external DAC.

 It sounds the exact same out of my mom's iPhone 5 to my ears. It also sounds very good (if not quite as good) out of my HTC One. That's another plus with this headphone, even though it's sound is bordering on high-end, it's not hard at all to achieve that great sound. 

Wonderful! It sounds like I've made my choice then, should be getting a pair within the month. Thank you for the help!

No problem! Excited to see what you think of them, though I highly doubt you'll be disappointed.

Brilliant review that I think is absolutely spot-on in every respect. I have a pair of M500s and Sennheiser Momentums and your comparision is totally accurate.
 
I have my M500s paired with a DX50 and they pair really well. Excellent review and, more importantly, not full of fanboy rhetoric, well done.

Yet to hear these, wonder how it compares to Beyer DT1350s, especially since 1350s are the best isolated closed portables out there, 

What you describe is very similar to what I am experiencing with the ML Mikros 90.  Have you compared the M500 and the Mikros 90?