I recently traded my HD600's for these cans *gasp* and although I was completely shocked by how excellent they sounded, I could not keep them as the comfort was just too poor. I found the ear pad materials completely sub-par, most notably in that they aren't breathable! That coupled with the tight clamp and shallow pads made these very troublesome for me. Keep in mind that I have tall ears that protrude significantly, a tall head, and a steep jawline though... For reference, I can barely get by wearing the Momentum M1, usually it's for short periods of time. For these I'd have to physically try to stretch out the elastic and pull my head right up against the steel outer rim to get them to stay anywhere near the bottom of my ears, and even then you could always feel the force upwards as it's very uneven across the ears.
I welcome others with smaller ears and heads however to pick these up because you'll undoubtedly enjoy them. The sound quality is remarkable for a closed can, I'll second Tyll's opinion on that!