I only have one complaint about the S500. It's the same complaint I had about the FX40s.
If you don't have a well mastered source, you hear every flaw and problem.
Listening to files of songs I had no problem with in the past I find myself suddenly saying "boy, listen to the artifacts in the high-hat and cymbals on that".
It's a double edged sword. I've heard defects in ultra respected audiophille recordings that previously left unnoticed. For casual listening when you want just to chill out and relax, having HA-S500 as sole headphone would be a (sado-) masochistic choice indeed. When everything upstream in the system is OK - WOW !
Problem is that condition is seldom, if ever, met in real life on music one likes best. We strive for perfection, but when something this close to it comes along, yada yadaing about defects in recordings of one's beloved music can be distracting, to say the least.
When time pressure eases itself a bit, I am more than one bit concerned just what JVC HA-S500 might unearth on my treasured LPs. Hopefully more good than bad !