The "Eggos", are these are known, are headphones designed primarily for portable use, as evidenced by the short+extension cord style, the supplied carrying pouch, and the ability to be folded up into a shape resembling an egg, hence the name. For that purpose, they do a nice job:

Comfort: these are circumaural, but they're among the smallest of that category. As such, some people's ears may touch the insides of the cups, causing discomfort. For the majority of people though, the fit is fine, and these can be worn for hours on end. There is one other small issue - the headband. They have a sort of "auto-strangle" function that comes into effect if you try to put the headphones around your neck.

Isolation: there is some, though not enough to make you oblivious to the outside world (so much that you miss the train stop being announced, for example). There is virtually no sound leakage - outsiders won't hear any sound unless their ears are pressed right up against the silver plastic "button" on each side, and even then, there is very little.

Sound: these headphones are a bit of a polarizing product in terms of their acoustic signature - people usually either really like them or really dislike them. The main reason for this is the bass - it's well-defined and clear, but there's very little of it. There are mods which supposedly alleviate the problem, but bassheads would still be well-advised to look towards other solutions. The mid and highs, by comparison, are these headphones' forte - smooth, clear, and accurate.

Overall: among all the portable headphones I've tried, these are still my favorite - though I've found I still prefer earbuds and (especially) canalphones for portable use. My taste in music tend to have little emphasis on the bass, so that doesn't bother me. The only problem is that these are Japanese-market only, the only way to get one if you live elsewhere is to import. AudioCubes.com and Minidisco.com are two well-known sources which offers them, but at $90, it's not quite the great deal that it is if you buy them at Japanese prices (around 7000 yen).