The Sennheiser HD-650s are some of the best headphones that the company has to offer, which is saying a lot because they have a great line of consumer and studio headphones.  While I have really only used these headphones a few times for listening back to mixes on, these headphones will work in pretty much any environment.  I'm not sure if they would be ideal for mixing on as I haven't tried, but as far as general listening and monitoring during recording goes, these will work great.  They are sturdy and have a great build to them in addition to the fact that I found them quite comfortable to wear.  While I don't personally own a pair of the HD-650s, a studio that I worked at had a pair of them and I would occasionally check mixes that I had done on them to get a new perspective on the mix.  While they could sometimes be deceiving since they have such a superb sound quality, when compared with a variety of systems they can definitely help you to see where your mix is at.  If you are a consumer looking for a great set of listening headphones to use with your iPod or MP3 player, this is will definitely be more than enough for most listeners.  The price definitely isn't what most people are going to want to pay for consumer headphones, so if you are looking for a cheap pair of headphones these definitely are not it.  I would recommend the Sennheiser HD-650s to anyone looking for a very high quality set of headphones to be used in just about any application.  After having said that, I would say to definitely try these out before you buy them to see if they will work for what you are trying to use them for!