I like them, they are well build and very comfortable. earpads and leather headband are great. Compared to my regular HD650 they are on the heavy side and sit a bit loose on the head.
They are darker than the HD650 with more bass and more clarity in the treble (read - more pronounced treble). It's very nicely V-shaped. I wouldn't describe the treble rolled, it's more a recessed upper midrange or lower treble. Tonaliy is somewhere between HD650 and Audioquest Nighhawk (leather earpads). People comming from a dt880 or simillar will find them very dark.
Bass is good and midrange isn't too coloured, less so then what the Nighthawk does. Treble is on the slightly harsh side, it's not as smooth as HD650 but still good. Nothing to be bothered about.
Compared to the usual contenders in the sub 200$ pricerange I prefer the Fostex over dt990 and k712. HD650 beats them if you spend a fortune on amp and dac. And HD650 is more neutral and "less fun".
Of course the Fostex likes a powerfull amp.
Is is possible to get replacements for the earpads?