I thought I'd update this thread with a mini-review of the iGrado headphones, which I just purchased ($49 on Amazon). I am new to high-end headphones and have not read any other reviews elsewhere, but these are so impressive, I wanted to write something.
In short, the iGrado phones immediately became my favorite listening device (along with a few complaints). Compared to what? 5-6 of the standard ear bud thingies you get with iPhones/iPods, one new Sony DR-BT50 (also just purchased), and some older Sony MDR-V300's, and a worn-out pair of Sennheiser PX 100's. Nothing great, but as I said, I am new to high-end headphones, and now realize I have some learning to do.
Anyway, there is an immediate striking difference with the iGrado, which I can only describe as a spatial clarity. Every instrument and voice is clearly identifiable in its own "space". As I said, the difference is striking and immediately noticeable. Honestly, I never suspected headphones could give such a good sound, and I am humbled by the experience: I am officially a headphone NOOB
I did notice that some material had some harshness in the vocals in a certain range, especially when there were also guitars or similar instruments in the same range (complex sound). I attribute this to either the phones themselves (understood that these are not the top of the line Grado phones) or the lossy encoding of the audio material: I use 128k AAC for my iPhones and Nano, but ALAC for my iPod video and iPod Classic. So there is definitely a possibility that this occasional harshness is caused by one or both of these issues.
Unfortunately, none of the material I tested with is "popular" or readily available on the web for comparison testing (the Japanese pop singer "Epo" is my vocalist of choice

, but OTOH as I have heard her stuff so many times with lesser equipment, it made the iGrado improvement that much more noticeable. I just did a comparison listen on one track, against the two Sony's, and while they are both good, the bass has a comparatively muffled sound, and there is a lack of that spatial clarity which I had never noticed until using the iGrado's.
The shocking thing is that these are the $49 "low-end" Grado phones! What on Earth will the good ones sound like?!? So, I am set to make yet another new purchase, a better pair of Grado's, but I have not yet decided which ones to try. Advice and/or discussion welcome. I am considering the SR325i or the RS1/RS2.
Oh, the down side: they are not comfortable. The headband is made of hard plastic that is slightly flexible but otherwise not adjustable at all. This hard plastic tends to press against my upper ear and cause discomfort. I tried wearing them on a two-hour walk this evening, but before the two hours were up, the discomfort was overriding the joy of listening and I couldn't wait to get them off my head. Maybe that will change/improve over time (have had them about 5 days now). I tried giving the headband a good stretch outward to relieve the pressure on my ears, and the little "iGrado" metal emblem/sticker on the top started coming off. Sigh... I did wear them while jogging the other night and had no problems. And I had them cranked up with some King Crimson at work the other day, and was asked by someone in another cube to "please turn it down". So they aren't "private" (is there a standard term for this?).
Summary: 4 1/2 stars (out of 5), 5 for sound quality, but losing one whole star for comfort issues and gaining 1/2 star back for "bang for your buck": this is a great value at $49!