Headphones create a false sense of space that doesn't exist. The reverb levels will be wrong, the bass response is off balance and the overall mix is not made with the "air" factor that is so critical for sound reproduction. Use the cans to do rough mixes, but the master has to be allowed to "breathe". Headphones are like playing in a vacume .... even the good ones give you the wrong impression.
They sure are complimentary though, huh?