These tiny headphones are excellent.
When fitted correctly (see below), all external noise is cut out and, with my Sony MD / MP3, I'm rewarded with strong (but not overbearing) bass; treble which has "presence" without being tinny; and crisp clear vocals.
Combined with their unique design - which makes them for me by far the most comfortable in-the-ear phones I've ever owned (plus, they never fall out!) - and I'm one v. satisfied customer...
One point to highlight: to ensure the best depth and clarity of sound from these little gems, it's important to use them with the correct size of (silicone) earpiece for your ear (S, M and L are supplied). They should be a tight, although comfortable, fit. With all external noise blocked out, you'll be rewarded with great sound. I highlight this because when using mine for the first time (with the medium earpieces that were fitted) I was dissapointed by the quietness of vocals and a bass that was too powerful. However, this problem was quickly resolved by my replacing with the larger earpieces.
Since I bought these phones for their sound quality - rather than the accompanying accessories - I won't comment on, for example, the small plastic carry case. Suffice to say, it adequately does its job but is easily lost.
Although not cheap, for their quality, I think these headphones offer good value for money. I'd recommend them to anyone looking for a comfortable, lightweight design, combined with outstanding sound.