NOTE: See the second post in the comments section for my updates to this review. New one posted for April 2017.

I don't use the word "revolutionary" casually. Truth is, a product rarely qualifies for that accolade. But knowing as much as I do about noise-cancelling technology, I would not have believed that what Bose has accomplished with the QC20 series was even possible. In fact, I'd say they've created the best all-around earphone or headphone on the market today for everyday use with portable music players. Note that I said "best all-around" which is not to say it's "best" in every category. If audiophile sound quality is your top priority, then look elsewhere, as both my Etymotic 4PT and Shure 530 series earphones sound better than the QC20s. However, those better-sounding 'phones have other drawbacks in actual use (more on that later), and they now sit in a drawer while the QC20s go with me everywhere. Bottom line: if you're looking for the best noise-cancelling on the market today, bar none, combined with very good sound, the ultimate in comfort and convenience, all in a very small, lightweight package, the QC20 is for you. This review will focus on a comparison of the QC20 with the QC15, as well as with the Etymotic 4PT and the Shure ES530, all of which I currently own and have used for some time. And please be sure to check out the "Design Flaw" section at the end of this review before deciding if the QC20 is for you.

Noise-cancelling: The QC20 is signifcantly better than my QC15. Look, I've used Bose QC headphones for years, but the QC20 actually made me gasp the first time I turned on its noise-cancelling circuit. I can only describe the effect as eerily silent, which seems impossible with an earphone that only lies against the opening of your ear, but doesn't go into the canal or encircle your ears like headphones. (By comparision, I never thought the noise cancelling on the QC3 was all that good.) In addition to achieving great noise-cancelling in an "ear bud" type design, Bose has also made real strides is quieting the sounds of speech, which--along with crying babies--have always largely evaded the capabilities of noise-cancelling systems. The QC20 is by no means perfect in silencing speech (or crying babies) but it's a clear step forward. My QC15s are going up for sale today.

Sound Quality: The sound of the QC20 is incrementally better than the QC15, but still lags behind the better in-ear 'phones like my Ety 4PT and Shure ES530. To my ears (Your Ears May Vary), the QC20 sound a bit veiled by comparison, and while the bass is certainly there, its quality and tightness just isn't as good. But let's put this in context: I"m talking about A/A+ sound for the Ety and Shure vs. B/B+ sound for the QC20. Plus, there are the drawbacks to the in-ear canal earphones: they silence outside sounds almost completely, which I find dangerous when walking the streets of NYC... and there's the incovenience of having to remove an earphone from the canal everytime you want to hear what someone is saying to you. The QC20 has an "aware" mode that allows in outside sound at the touch of a button. Also, with the Ety 4PT, I hear the microphonic thumping sound of the cable hitting my body when I walk--not as bad as earlier generations of the Ety cable, but still there. Finally, neither of these in-ear 'phones are comfortable for long-term wear, such as a cross-country flight. Again, Your Ears May Vary, but I have to remove them after a couple of hours.

Comfort: My QC15 headphones are certainly comfortable, but the soft silicone of the QC20 ear tips rest so comfortably against your ear openings that you simply forget you're wearing them at all. Most importantly, the Bose StayHear design of the tips keeps them in place, which is a huge deal for me. I have never been able to wear any ear bud design (and I think I've tried them all) because they fall out too easily. The Bose remain secure, but without force that would cause discomfort. The QC20s come with medium tips installed, but also include small and large sizes in the box.

Size/Weight: This is where the QC20 really trounces the QC15. The earphones store in a soft pouch that measures just 2.75 x 5 inches and they weigh next to nothing. As nice as the storage case is for the QC15, it just looks huge by comparison. I was concerned that the "battery/control bar" at the plug end of the QC20 might have size and weight that would make it clunky in use, but it's small, very thin, and almost as feather-weight as just the cable itself. The bar measures just 1"W x 3.5"L x 1/4"D. Weight is only 3/4 of an ounce, including the end cable and plug. That end cable is just long enough to allow for easy folding of the bar against the back of your phone or music player and easy insertion into your pocket.

Convenience: Minimal size/weight make the QC20 a "take everywhere" earphone. Includes a super lightweight lithium battery that runs for 16 hours on just a 2-hour charge from USB. (Bose includes the required USB to micro-USB charging cable.) The earphones will continue to function with a dead battery, but without noise-cancelling and with somewhat degraded sound quality... still, better than nothing. The integrated microphone makes it a perfect headset for use with iPhone and other cellular phones. (Note that you must order the QC20i for use with Apple products.) The microphone also includes an "Aware Mode" switch that allows in some outside noise, like traffic sounds--convenient AND an essential safety feature if wearing these in a city environment.

Design Flaw: The silicone eartips do not simply slide on and off the earphones. There are two slots cut into the silicone that fit over two small plastic tabs on the earphones and hold the eartips firmly in place. When trying to change the medium eartips to the small ones, I broke one of those tabs, and this was after reading the instructions, and following them as closely as I could. Bose provided an immediate exchange for me, so no problem there, but if you buy the QC20 and need to change the eartip size, I'd recommend getting on the phone with Bose customer service, which is superb, and let them guide you.

One final tip: if you buy directly from Bose, either online or at one of their stores. you get a 30-day, no questions asked, money-back guarantee they don't offer if you buy elsewhere. Use the 'phones all you want and, if you're not satisfied after a month, just return them for a full refund. Since new models of Bose products are never discounted anywhere, that risk-free trial is a big advantage to buying direct. Just be prepared for the fact that you will NOT be sending these earphones back! ;-)

Bottom line: overall, the QC20s are five star earphones with an asterisk due to the plastic tab design. Thanks for taking the time to read my review and I hope you find it helpful in making a buying decision. Again, if you look at the second post in the comments section, you will find my updates to this original review.

I was going to give these four stars, but then realized that if you are looking at these then you are interested in the an earphone that cancels out the background noise and in that department these are unbeatable.
On our last airplane ride I recorded the background noise and created a loop to play back on my hifi system. This gave me the opportunity to compare several earphones in a controlled environment. The etymotics with passive noise reduction did well, other active noise reduction earphones also did varying degrees of reduction in the background noise, but none could match the phenomenal quietness achieved by the BoseQC20s.
The star I would have deducted would have been for the sound quality, which to my ears isn't quite as good as other earphones that have noise reduction capabilities, but the enjoyment of the superior sound from the others is degraded by the intrusion of background noise, especially in the quieter passages. The overall sound of the Bose was the clear winner and I have kept these as my travel earphones.

I didn't buy these for air travel, and I didn't buy them for listening to music. I bought these as an act of desperation. I'm a very light sleeper, and I sleep at odd hours. I also happen to live in a noisy city (Chicago), and in an noisy part of the city to boot. I've been driven to near-madness by chronic sleeplessness. Enter these little earbuds. I was hesitant to spend the money because I didn't think they could possibly do what I needed them to do. I need them to drown out heavy construction noise one floor above me. I need them to drown out the infernal din of four days of Lollapalooza every summer (which takes place just outside my windows). I need them to make the city go away sometimes. Incredibly, they do all of that and do it well (especially when used in conjunction with a white noise app). And unlike NC headphones, they are really comfortable to sleep in. Like I said, life changing.

I have an original pair of Bose over-the-ear QC-15s, which are comfortable, provide okay sound, and great noise reduction. I ordered these in-ear QC-20s primarily because they're far less bulky to carry on an airplane. But holy @#$#$ are they amazing. The sound quality is outstanding, and the noise reduction blows away my old over-the-ear QC-15s, which I didn't think was possible. They're also quite comfortable. The little in-line switch that lets you selectively disable noise reduction is a nice touch; I'm surprised at how helpful it is/how many times I've used it already. I think these are the best headphones I've ever owned, of any kind. Numerous reviews here point to their relative fragility, and although mine are still new, I'm treating them gingerly and feel they need it. For example, the square-cornered/sure-to-snag-on-anything battery pack is *hard-wired* to the unit on both sides; there's no plugs/jacks and thus no safe breakaway capability. I hope these things hold up as good as they sound; for now, they're simply awesome.