I'm one of those who always bring up the treble spike - for me even at low volumes it can bother me a bit. Mind you its a matter of perspective and what one is used to. For me I prefer a fuller bodied, mid oriented sound when going for Rock, Jazz, Metal. I prefer headphones like the HD800 / T1 for classical stuff. I don't really care much about or worry about how accurate tonally something is, I just go for what I feel the most impressive sound and most enjoyment from with a certain type of music. Whether or not this disqualifies me from being able to discuss headphones in someones eyes is their choice or not - for better or worse - I cannot do this anyway not being a musician and not attending many acoustic performances. I know many who love the TH600 for metal, but for me it seems thin - but that is my perspective when coming from more mid oriented/forward cans. Likewise some prefer very bright and upfront headphones for metal, while my ears are too sensitive to the treble for that, and I go with darker thicker sounding cans like the LCD2. To many my choices for rock and metal might seem slow and too laid back to be exciting, so be it and nothing takes away from that opinion as its just as valid. I only go the way I do because I have problems with many modern recordings of such styles which are extremely fatiguing with brighter phones - and I tend to listen in the range of 75-80db so not quiet or anything - many listen lower. I won't give up these albums which are not the best recorded, as I cannot give up the music I enjoy.
Likewise, for electronic I've always preferred a type of U shaped or at least bass heavy signature (not super heavy though/not boosted with eq), some will place more merit on the midrange of the can for electronic as that is where the half of the music is if not more.
Mind you I'm a big TH600 fan overall, I'm not trying to sound highly negative or anything. The treble spike is not a deal breaker for me, and its a problem say 2/10 albums in my collection overall, just notable. I can still enjoy other genres with them, just not as much as some of my other cans with the styles.