I originally bought the ATH-EQ66 to use when travelling. They were cheap (about ¥2000/£10) and I wasn’t planning to do any serious listening with them (I have Yuin PK1s for that, or Shure EC3s which I still can’t decide if I like or not.) I listen to audio books a lot and have been using the Nokia Labs Audiobook application, which is probably the best “feature” of my N73.
I was pleasantly surprised at how good these clip-ons are. While the sound is nothing special for music, it is listenable. The clip-on design is not well suited to high quality sound, it’s more about convenience. For the spoken word they perform quite well. Despite having little to no isolation you can understand what is being said even on a noisy train or aeroplane. They don’t seem to leak sound too much either, important if you use public transport.
Best of all they are very easy to carry around, having a build in cable reel that the main cord zips up into, with a socket to store the plug all built into the left can. Despite this they don’t seem bulky at all, don’t weigh much and are rugged enough to just put in your pocket. They are comfortable too, and don’t have any problem staying one. The single cord is easier to work with than a y-split too.
The only issue I have with them is that they do seem to be marginally harder to drive than the Yuin PK1s, although perhaps it’s just that they are not as direct. Either way, I need the volume a bit higher than with the PK1s, and on some very quiet audio books that means pushing my phone to the maximum level when in a noisy environment.