I just started playing around with my new earphones, purchased at the recently remodeled Apple Store Eastview with my iPhone rebate. I grabbed a pair of Shure ES210 earphones to use at work for isolating myself from the disgusting bodily noises eminating from the surrounding cubicles and they sound fantastic. This is my first pair of in-ear earphones and I have to admit, I'm impressed. I had been hearing for a while that people were getting amazing levels of noise isolation with ear canal headphones but I wasn't completely convinced until I put the E210s on.
At the moment, I just have the earphones plugged into my PowerBook where I've got a smart playlist in iTunes with every lossless track on shuffle. The intro to Dark Side of the Moon really makes you think you're going insane when the sound is inside your head. The background noise from the PowerBook's sub-par audio chips is a bit annoying, but it doesn't seem to be nearly as present as it is with my HD515s.
I really don't have much else to compare them to other than my Sennheiser HD515s so I guess I'll do that. From HeadRoom's frequency response graph, you can see that they're two very different listening experiences. The ES210 earphones really are much closer to monitor headphones as they have a very flat response across most of the lower frequencies whereas the HD515 headphones add a lot more "personality" to the sound, which I've really grown to like. I was surprised that the noise isolation of the ES210 wasn't much better than the HD515. The earbuds are certainly a different type of isolation and, in some respects, better (no bulky cans hanging off my ears) than the HD515 but I have a feeling that they're about on par with the level of noise that they block out. I'll definitely need to try the ES210 out in some noisier conditions before I make a final judgement though.
Overall, I'm really enjoying the ES210 simply because I get a very high quality sound reproduction without having to carry around giant cans. Now I just need to find a better source... Does anybody know where I can get a decent Sony Discman?