I ordered a pair from Amazon and just got them today. I am very impressed. All I can compare to is the HJE900 and the TFTA 2100-3v2b, and I think both get destroyed in comparison. I guess it may be my personal preference, but the yam's are not bass light at all, no sibilance or shrillness, no recessed or laid back mids, and definitely nothing being muffled or smeared with mid bass: as in comparison with the other 2, especially being in the same price bracket. All of this straight out of the box too, and I'm sure they will improve over time, even if only a tiny bit. In addition I find that they are more forgiving with bad quality mp3s as well. I mainly listen to EDM, so I can't comment on any acoustic recordings.
These were purchased as a "try-out" pair, and if weren't liked were going back, but these are definitely keepers.
Not sure if I helped anyone with my comments, but I have to agree with the review being spot on, and for the price one cannot go wrong.
No problem driving them from a 4s, and as the pic above shows, they are very tiny.