Comfort is essential for a headphone. Unlike other audio gear you wear a headphone and if you don't enjoy wearing it then you won't enjoy it regardless of how great it sounds. That's why I understand why some hate Etymotic IEMs, as their deep fit isn't for everyone and I do understand why some just don't like them. Clamping force, stability, contact point feel, earpads, cup shape etc all make a difference, and especially weight. I just can't get on with the Audeze LCD family, it makes me sad as some of them sound very good but I just find them heavy and uncomfortable. Conversely, I find most Beyerdynamic headphones I've tried to be wonderfully comfortable even with that Beyer treble thing.
Easily replaceable pads, I also think replaceable cables are important, preferable with a standard jack type connection. I must admit I like nice quality materials and premium feel, but on the other hand I do also acknowledge that the Sennheiser HD580/HD6xx family are probably amongst the most rugged and durable headphones out there based on my experience with the 580's despite the low rent feel.
For sound signature, that one can vary. I like a flat and neutral sound signature (I love my ER4 SR IEMs) but I also like more coloured tuning when I'm in the right mood. The Sony MDR Z7 is a bit like a "Beats lite" headphone, but I do like my MDR Z7's. And I love my ATH MSR7's despite them being slightly bright.
Easily replaceable pads, I also think replaceable cables are important, preferable with a standard jack type connection. I must admit I like nice quality materials and premium feel, but on the other hand I do also acknowledge that the Sennheiser HD580/HD6xx family are probably amongst the most rugged and durable headphones out there based on my experience with the 580's despite the low rent feel.
For sound signature, that one can vary. I like a flat and neutral sound signature (I love my ER4 SR IEMs) but I also like more coloured tuning when I'm in the right mood. The Sony MDR Z7 is a bit like a "Beats lite" headphone, but I do like my MDR Z7's. And I love my ATH MSR7's despite them being slightly bright.