Love them 
I bought this product about 18 months ago and use them everyday. They are high quality, very comfortable and simply a great product. I tested all the noise cancelling phones I could find and these were the best overall. Highly recommended.

 Again - Bose QC3 
I had not doubt buying again QC3 after my old Bose was stolen. The choice was clear for it outstanding noice cancelling system. They are specially helpful on long haul flights (I do plenty of business travels).

Four of my collagues purchased Bose after testing my set.
This is best recommendation.

Artur

 $50 lithium battery fell out twice and had to be replaced; this $350 headset has already cost me an extra $150. 
The headset requires a $50 battery. It fell out of the headset twice in a little over a year. I am going to have to buy a new one for the second time. Although I explained the situation to Bose, twice, they would not offer a replacement despite the fact that this clearly should not have happened.

A few months ago, I had to get a replacement connecting cord from Bose when the one the headset came with stopped working.

The battery also requires a charger, which I lost (my fault, but it's rather small), but it was another $50 to replace that. So on top of the $350 I spent, I I've already spent an additional $100 and will be spending another $50 for a new battery.

The headphones work reasonably well, but they are heavy on the ear and rather unsightly.

 Overpriced underperformer 
I recently tested the mighty and ubiquitous QC3's, though the sound reproduction, as well as the noise canceling quality, is not as class leading as one may think. The clarity, and definition across the frequency range was stale with muted mids, boomy bass, and treble that grated like nails on a chalk board at higher volumes. Between classical -"Pavarotti", acoustic -"Seal Unplugged" and dance music -"Justice D.A.N.C.E." genres played, they fared best with the acoustic genre. Source used was a 1st Gen iPhone with the tracks encoded at 320kbps.

The strong point of these headphones is the noise cancellation at altitude. Great to kick back and sleep.

However music playback suffers as a result with a very ordinary sound stage that seems muted. The build quality is good, and is great for domestic use. However, the design is not particularly durable or conceived with travelers' needs in mind, i.e. continual inspection at security checks. In fact a friend has had a ham-fisted TSA agent crack the part of the plastic holding the ear-cups while inspecting the rechargeable battery and it's bay... simple AAA's would have been much more practical, as well as a more robust design spec.

Conclusion, overpriced under-performer. They would be appealing at a $125-175 price point, IF the active cancellation was accompanied by equivalent acoustic excellence. Competitors have blown past Bose with better offerings. For audiophiles Sennheiser PXC450's are "non plus ultra", PXC350's are also worth a look-in. For hipsters, the Monster Beats are also superior with stellar music reproduction, but the active noise cancellation somewhat less intense. THANKS FOR READING and good luck with whatever you buy. : )

 Bose Headphone 
Bose? QuietComfort? 3 Acoustic Noise Cancelling? Headphones
Highly recommended. It is an awsome headphone that I have never had.