sennheiser are a very good brand for audio goods, and this headset is no exception, one of the most expensive sets around, you can tell the quality just by the feel of the thing, it's nice and solid, not chunjky but not flimsy either, the boom microphone is flexible, but sturdy enough to remain where you put it. the microphone records sound incredibley clear, when using skype i always have people asking how i got it so clear :)
the cups of the headphone are very comfortable to wear, but the problem is after an hour or so of prolonged use.. the insides of the cups can become a little damp, and there is a slight pressure on your head. certainly tolerable if you plan on using it for long sessions though.
soudn quality is good for the most part, but the lower range of sound tends to suffer from a slightly weak bass, not a problem for most people as you can just increase the bass in your mixer, but certain Laptops with basic onboard soudn will find that they can't do that, and so the sound is a little flat, but again still perfectly clear.
overall, it's performance for a price.. they certainly aren't the cheapest of headphones, but the quality is evident (both in the microphone and in what i have to so is the most complicated piece of packaging i've ever seen!). for best results, you'll need to manually boost the bass a little to even things out.