They are not good to mix world class mixes with. It doesn't sound like you have mixed it, when you later on listen to other common speakers. The sound is alright as one sound. But I wouldn't recommend to mix a final mix with these headphones. But strangely enough they are very good to listen with when you use a Maximizer. Than you can hear the little details that are wrong.
As headphones to listen to a cd, they are great. I use them also when I produce, and it works fine. But a final mix, no way. They don't give the truth about how it will sound on common speakers.