Rating: 
Summary: Great for airplane use
Review: I fly frequently to Europe and had been debating purchasing noise cancelling headphones because I doubted that they would work well. After doing much research I picked the Sennheiser PXC 250 because they are portable, unlike the Bose, and they are 1/2 the price of the Bose.
I was really surprised how well the headphones worked on a plane. With the inflight audio system, I actually had to lower the volume because it was too loud. This had never happened before. I even used the headphones disconnected from the audio system to sleep and it was the best I had ever slept on a plane.
These headphones are not for casual listening in quiet environments because they inject white noise, which when on a plane, is not noticeable, but in a quiet environment, can be readily heard.
The "cigar" case is a little annoying but it fits easily in a shirt pocket. Also, I would have preferred a single cable going to the headphone speakers rather than two (one to each ear).
I did not experience the nausea that other reviews complained about.
Overall, I was very pleased with my purchase and would highly recommend the headphones.
Rating: 
Summary: Decent but overpriced!
Review: I recently got the Sennheiser PXC 250 after a lot of research. This specific product has been very positively reviewed in many technical publications. When it arrived I was impressed at the packaging of the headphones and latter I really enjoyed the sound quality, especially with the noise cancelling active that actually amplifies and colors the sound. The sound cancellation on the other side is minimal....of course mainly in the lower frequencies. What put me off is really the fact that in my third day of use the headphones started having a bad noise when active cancellation is activated. Very annoying! I was hoping for better quality control from this quite expensive headphone that got broke in my third day of use. Yes, they are going for repair....but needed repair so soon??? I wonder how long are they going to last. The design appears cool but the fit and finnish does not appear solid. They make you feel they are going to get damaged soon and not last long.Plus, the cord is VERY short and definitely limits your listening distances. While the sound quality is really good indeed, it definitely does not justify the retail price these babies are being offered for. If you can get them discounted give them a try... otherwise full retail price is not what they are worth.
Rating:
Summary: Excellent sound, but noise-cancelling causes nauseousness
Review: After 5 year's ownership of my Sennheiser HD525's, I decided that when I was going to look into noise-cancelling headphones I'd turn to Sennheiser first. The sound-quality of the PXC250 is excellent for a headphone in this size, but I had a major issue instantly with the noise-cancelling feature. I tested my new headphones out for the first time at work. Sitting in my cubicle I was listening to Nora Jones. It's a great CD to test speaker quality - the voice recording of Nora is clear and precise. The noise-cancelling system worked great in cutting out background noise, but after 5 minutes of enjoyment I became nauseous. I felt this harsh pressure in my inner ear and for some reason it was affecting my balance. I became light-headed and dizzy. I immediately shut off the noise-cancelling system to see if that would help. The pressure in my ears was relieved but I was left with a tenseness in my throat: the same feeling you get with an over-tightened tie around your neck. For the next hour or so I was feeling this pressure in my throat. It was similar to the feeling you get when you want to throw up, but of coarse not that intense. A year ago I tried on a David-Clark noise-cancelling headset for my private-pilot training. I was impressed with their ability to cancel out noise, but I never felt this pressure in the inner ear. Maybe I did not try them on long enough. Conclusion is, try the Sennheiser PXC250's out before you buy them. If the noise-cancelling feature makes you nauseous, settle for traditional pair of Sennheiser headphones. For those who do not have the problem I had, buy the PXC250's - I highly recommend them. Their noise-cancelling system works excellent and the quality of sound that these headphones produce lives up to the well-known superior quality of the Sennheiser product line.
Rating:
Summary: Great for Airplane Use
Review: In summary these headphones are amazing for airplane use and I definitely recommend them. They are a great gift for frequent flyers. I was sceptical about the PXC 250's ability to suppress outside noise, especially during flying. When I put them on -- Wow! They greatly reduced that airplane droning sound. They also sound quite good. Curiously I found that considerable noise was reduced without the noise suppression on, perhaps 80% of the total effect. I'm curious what others think. I have never found any pair of headphones that I could comfortably wear for hours which I believe is true with many others. Same is true with these. I also agree with a few others that the noise cancellation creates a feeling of ear drum pressure which I found somewhat uncomfortable. Size is good for travel. All in all I am happy, no GRATEFUL, to have these headphones.
Rating: 
Summary: Awsome sound + great noise cancellation + comfort...
Review: ...All in a small and portable form factor.
Very well built, well balanced headphones.
It does not get any better than this folks! If size and portability does not matter and you can spend a bit more money, then try the Sennheiser HD650.
Rating:
Summary: Best noise cancelling headphones
Review: I have tried a number of noise cancelling headphones and I like this most. Nice collapsile design, good fit on years, handy bag to take it with - with all necessary accesoires. Car/plane noise is being cancelled really well. I can't see a difference with more expensive and heavy Bose. Sound quality is also good - hard to wish more in a noisy place. Note that this headphones are designed to use in typical low frequency noise like planes. If you want to use it just like a regular headphones at home, look for a different kind.
Rating:
Summary: It is okay but NOT GooD enough.
Review: The headphone is well designed, light, fairly comfortable to wear. However the noise cancelling part is not as expected. It appears that noise can only be reduced by about 60%-70% on plane,or on a noisy street. Ear cups for sure ard too SMALL and the quality for Stereo music listening operation is about the level of a $25.00 Sony Headset.
Rating:
Summary: Good sound, moderately effective, flimsy
Review: I've used the headsets for about 20 flights so far. I chose them in preference to the Bose noise-cancelling headphones because of 1) cost, 2) comfort, and 3) sound quality. They proved to be very convenient (for music listening, as well as noise cancellation). Not nearly as good as suppressing noise as Bose set, but this is mostly due to construction--the Sennheiser are light and fit over the ear; the Bose are heavier and surround the ear. On the other hand, these are more comfortable to wear (less sweating, and can also hear the flight attendant). The sound quality is very good, and it works even without batteries. My biggest complaint is the switch broke after 6 months (I have to poke it with a toothpick to operate): it uses a very thin plastic connector. I wish this part, which moves all the time was a bit sturdier. --inotherworlds.com
Rating:
Summary: Dreamy addition for this music fiend
Review: Twice as good for less than half the price of the Bose noise reduction headphones. Fit nicely and feel great but mostly they really block out most of the ambient noise. I really love everything about this headphone. Also, note that it comes with a 2 year warrenty, better than most other headphones.
Rating: 
Summary: very disappointing design
Review: While the noise reduction circuitry works fine, it is of little use considering the flawed design. The ear pads fit ON instead of over and around the ears. This not only lets in background noise but also gets pretty uncomfortable after awhile since you have to have them as tight as possible to get any noise reduction at all. Until Sennheiser has the sense to use a more sensible design, stick with the cushioned sets that go over the ear for comfort and keeping out more noise.
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