I really hate those headphones that hook around your ear or behind your neck, so finding a suitable alternative was a bit of a struggle. These, so far, seem to fit the bill. They fit in my ear perfectly (there are three sizes, both for the little hook and for the yellow in-ear bit, so they are fairly adjustable) and never fall out when I'm running.
In terms of sound quality, I am not particularly qualified to hold an expert opinion but they seem to do it for me. I don't need to go full volume which was a decisive factor, seeing as I exercise extremely often and for relatively long periods (1.5 to 2 hours a session). They isolate background noise enough but not completely, which I think is a positive thing - it is dangerous to exercise without ambiant noise, such as incoming traffic.
The only downside, I would say, is the length of the cord - the short one is too short (unless you have one of those upper-arm bands to fit your music player), and the long one is - you guessed it - too long. I imagine the long one was designed to reach to a waistband contraption of sorts where you'd fit your iPod. I happen to just hold my iPod when I'm running (it's an old iPod classic so fairly chunky and not appropriate for all those waist-, wrist- and arm contraptions), so I just twist the cable extension around my fingers and it's fine like that for me.
The little volume control on the extension cable is quite handy. The extension also has a clip - I use it when I am on the crosstrainer, it gets in the way when I'm running.
Ah, one last thing: all the dudes tell me the colour is very cool.
I'd recommend this for people who, like me, can't stand 'round the ear' or 'behind the neck' sports headphones. They are extremely comfortable. After a month of use, I have no issues to report. The price is reasonable for the quality of the product. On the whole, I am extremely pleased with my purchase.