Compared to nothing (in the way of noise cancelling) these are better than that.
Damning with faint praise?  Yeah, I guess so, but really what can you expect for the price.
Sony makes a product that generally is worth buying, if it meets your criteria.
If in this case the criteria is cheap, light weight and easily portable you are in luck.
If it is for noticeable noise reduction, again you are in luck.
If you have any pretensions of being an audiophile, and getting high quality audio, well, that's not going to happen.
These do offer some noise reduction, and being on ear, as opposed to over ear they really can't isolate much. 
I would say, bump your budget up to closer to, but still under $100, and you can find much more effective noise reduction, as well as better audio.
These are barely acceptable, and then only for non-discerning listeners. One feature I appreciate is the use of a replaceable AAA battery. And the long life these give using that one battery.

There seems to be a lot of issues with the sound quality for these 2nd gen Bose phones.
These came out before wireless headphones were in any significant use, and when few other companies were making a serious attempt at noise reduction.
Given the parameters that Bose used, which was the best travel headphones and good quality audio, I know they succeeded and excelled over other products. 
In fact they had no real competitors for quite some time. Virtually every review was glowing, and considered them the gold standard. 
Today, is seems unfair to judge them against other products, with a higher price, and with years of development to improve on the Bose product. Or, against wireless head phones. 
Taken just on their original merits, and in the time frame they were introduced in, these were unbeatable. I feel that for the money they are still a best buy.
The absolutely have amazing noise reduction capabilities. They have unparalleled battery life, and not insignificantly, use replaceable AAA batteries.
Their portability, by which I mean the beautifully designed case they fold into, is top notch. The case even has room for a spare battery and airline jack. Possibly the standard for well designed cases.
Here's the test- take a flight, carry these along, plug in your own source, and even use an amp. You will be very pleased. It's that simple.
Do not expect to get the best possible audio, since you are in a noisy environment.
Do not expect them to compete with newly designed $400 head phones. That's not even logical. They were engineered years ago and yet are still excellent for traveling.

I am not an obsessed audiophile, but have enjoyed headphones and music in general, for a very long time. Only recently, in the last 3 or 4 years, have I had been buying high quality headphones. I prefer closed over the ear, but since I enjoy them mostly at home, by myself, open are fine also.
I listen to a lot of jazz, both old and new school, and also blues of all types.
I do not travel with headphones very often, and never use them for commuting, since I am retired.
I have been using these for a couple of months now, and have used them amped with a couple of different pieces of gear, as well as straight from a music player, and straight from a CD player, without an amplifier.
What ever I have listened to I have been very pleased with these, perhaps as much or more as with my planar heaphones, which are my standard for great sound.
It is obvious that a LOT of time went into the design and aesthetics of these. Also a significant amount of time was spent getting the sound just right. I agree with others who have talked about the amazing design, which is unequaled in my experience. I find nothing to criticize about these.

Brand new to the whole world of portable amps, but a really long time hifi addict.
Bought this unit on recomendations of others online, and am not disappointed. I have nothing to compare it with of course. I am waiting for a converter to use it on my iPod proprietary slot, so I have tried it only on an Android phone and a Sony MP3 player. I have a variety of headphones, from Sennheiser to mee to Koss, and I must say the sound improvement is quite noticeable. Very pleased with the features, ease of use and available output improvement.