I'm sitting here listening to my SanDisk Sansa Clip+ 4 GB MP3 Player (Red) with these headphones attached as I write this review, so the sound profile of these earbuds is quite fresh. I also believe I have good hearing as a musician of 12 years, so my review will be in a technical, but graspable, format.
To me, there are three main categories to rate any listening device, and across four ranges. The categories are Detail, Presence, and Coverage. The four ranges are Bass, Low Middle, Middle, and High. I think this way of describing can make the idea of audio equipment accessible to lots of people who don't yet understand esoteric and obscure ways of describing audio equipment that some people tend to make up off the top of their heads. Then of course there is build quality, but that is separate.
The four ranges are fairly self explanatory. "Detail" means how much of your music you can hear, like a light crash of a hi-hat, faint bass guitar notes lost in a sub-par mix, or the sound of a backup singer behind the instruments and lead singer. On good audio equipment, you'll hear things you've never heard before. "Presence" is how well that range stands out by itself. Ideally all four ranges should be balanced so that each stands out equally, and so that for example the high guitar and cymbal sounds don't drown out the lower bass or vocal notes. "Coverage" or 'attack' is how smoothly the music comes onto the soundstage, which is a function of how responsive and high-quality the audio drivers in the audio equipment are. If they're low-quality, things will sound very "fast" or "sharp" and end up giving you a headache. Many of the instruments will sound like they came out of nowhere and you'll get listening fatigue very quickly.
These earbuds have some of the best Low Mids and Mids -- where the majority of frequency response in music lies -- that I've heard out of any earbuds in my life. They may even beat out my $250 Etymotic buds that I no longer have. Detail is fantastic: guitar solos are clear and crisp on every note, vocals come out like the person is singing right next to you, and synth work is vibrant and full of life. Presence is perfect, everything across the Low Mid and Mid range is easy to pick up on and distinguish. Coverage is also spot-on in this range. You hear the rise and fall of every note properly just like you were playing the guitar yourself. You can even distinguish what kind of pick and picking technique is used on a lot of songs!
The Highs and Bass are where these earbuds start showing why they're priced the way they are. Both are good, but not excellent like the Low Mids/Mids. The biggest problems with the Highs are the Presence and Coverage. Many of the cymbal crashes come out very loud and overpower the rest of the music for their (fleeting) duration. If there are many crashes in a row, it can make you want to take the earbuds out of your ears. The Detail is also lacking on the Highs. Some higher guitar notes and many cymbal crashes again seem to disappear without warning upon resolution. The Bass is also severely lacking in Presence and Coverage. The Detail is good, notes are distinct, but there is not much Bass response. The Etymotics I had sounded like I had a tiny subwoofer in my head. These sound like I have sub-$100 earbuds in my head. The Bass is cutoff somewhere between 80Hz and 120Hz, and there's no response beneath that. It's disappointing when you're trying to figure out a bassline. It's still pleasant to listen to and isn't harsh like the Highs can be, but the Detail just isn't there.
There are also some build quality niggles. There is a moderate amount of cord noise whenever it's moved, which makes them a poor choice for exercising. These are best suited for car rides, slow walking, trains and planes, etc. The cord also is pretty low quality, and tangles a lot, and also seems like it will eventually break. So far so good though. The earbuds do fit well in your ear, and are generally a pleasure to wear.
However, again, the whole middle range of music is astounding. They are definitely worth keeping just for that. They make it very easy to get over the lacking Bass response, and perhaps just turn down the treble in your mp3 player's equalizer to take care of the harsh Highs. To note, these are trends I noticed over about 10 entire albums, from different artists, so it's not a problem with just one band or kind of music. Luckily, that also means the great mid response will come through with anything you listen to.
I know this is a longer review and I hope I really helped you if you made it this far. These are excellent earbuds for general listening and overall outclass their pricetag by multiple times. Just take the boat load of 5-star reviews with a grain of salt and don't expect monitor-quality earbuds, and you'll be extremely pleased as long as you don't torture-test their build quality.