I use these headphones for mixing and a bit of mastering in my current studio situation. I spent hours listening to different genres of music to get a feel for how they translate and I was extremely pleased.
They offer great stereo imaging (some would say too wide, but you can use that to your advantage) and clarity both in terms of detail and in terms of frequencies.
I would say they're not the most comfortable of headphones. I'm speaking mostly in regards to the headband. They're not nearly as comfortable as, say, a pair of Beyerdynamic headphones. That being said, I'm sure they'll loosen up a bit with time, and if you take regular breaks (which are useful anyway to avoid ear fatigue), then that will not be a serious issue whatsoever.
Bear in mind that you will need to be extra cautious if you're planning on using this to track (or record) as well, as they're open by design, and do let sound spill out. This makes them more suited for the mixing/producing parts of the job.