I think KEF represents a new face in the portable headphone/IEM market that deserves some appreciation. In light of this I thought I would start up this thread.
Here are the existing threads, reviews, and information:
Fullsize KEF thread: http://www.head-fi.org/t/661032/kef-new-headphones
At this point in time I own the M500 and have a pair of M200 coming in.
The M500 is the most neutral on ear headphone I have owned and also the most comfortable. It offers an extremely true to the music sound that is actually detrimental if you use lower quality music and can show issues with your source equipment as well. In my case I generally use my Nokia 920 phone for portable listening and with this phone, the M500 has a bit of an upper midrange peak that needs to be adjusted for these to sound right. Off my old iPhone 4 or my Ipad mini these sound exceptional as well as off my new laptop.
If you look through one thread listed above you will find the most information on the M500 along with all of initial comments and comparisons. As it stands today I am confident this headphone is at least as good as or better than the DT1350 sonically while being more comfortable and it crushes the VModa M80 unless your a midrange lover only.
I will post a full review on the M500 hopefully sometime over the next week and will do the same for the M200 when I have it on hand.