I am very pleased with this Sennheiser.
It is almost perfect in every way. comfortable enough to wear for hours and the sound is crystal clear.
If you're looking for thick bass, this might not be the best choice. Here the bass is just nicely balanced with the other frequencies. There is a small increase in the high bass (around 250hz) and the low mid (500hz) which makes the whole a bit too dark for my taste, but this is easily solved with an equalizer. I myself do 125hz -2db, 250hz -4db, 500hz -2db and 2khz +1.
This makes the whole thing just that little bit cleaner and brighter.
Women's singing voices in particular sound phenomenal. I myself like to listen to pop, rock or country like things like avril lavigne or the band perry. They come into their own with the hd599. I often listened to good quality music in ears before and that all seemed fine until I heard this sennheiser. In one word "amazing"!!
They are fine to use with portable devices or directly in a computer or laptop, but there is still a lot more to get out with a good amplifier or sound card I have noticed.
All in all, I would definitely recommend the hd599 to anyone looking for a natural and clear sound for their music.