Just got my KEF M200 in today and it's a great early Christmas gift. The sound is so smooth and wonderful RIGHT OUT OF THE BOX! No burn in time at all. I can only imagine where these end up after they have been baked for 50-100 hours of intense burn in???
I believe, if memory serves me well, that these are the best sounding dynamics right out of the box of any IEM i've ever had the priviledge of owning, and this includes the Sennheiser IE800, Fidelio S2, JVC FXT90, and HiFiMan RE-262.