Having listened carefully to the RE2 I have to say I am disappointed. My expectations were probably too high based on reviews, but IMHO this is no giant killer. Midrange is OK, but highly over-emphasized, and the top end rolls off around 6-7KHz, if I am any judge. Bass exists, but is so shelved down as to simply over-emphasize the mids. If I only listened to acoustic guitar these would probably be satisfying enough but I really expect full frequency response from anything with aspirations to be better than mid-fi...
By contrast, iPod direct or with the iBasso or DACPort, my Apple IEM's with a Mic and "tweaked" tips ("sawed off" mushrooms from my Shure collection, the stock silicone tips from Apple were too rigid to seal right in my ear), the Apple IEM simply blows the RE2 out of the water for engaging, detailed full range performance and for only a few $ more (yes, their midrange is grainy, not ideal but for $ it's good). Comparing to higher end IEMs like the SE530, as some have done, is simply no comparison. These high-end generic IEMs are vastly more revealing and natural and have a sense of engaging transparency that pulls me into the music instead of emphasizing the transducer.
Compared to the Sennheiser CX500s the 500s are sizzly with their over-hyped top end and grainy midrange, but at least they are full spectrum, and for knocking about the gym or washing the car, are more enjoyable to me driven direct off the iPod (and I don't think too highly of them, they're just cheap and reliable enough to last 1-2 years of abuse, which was what I thought I'd use the RE2 for).
Lastly, the RE2's tips are really hard to change, none of the stock ones fit me snuggly (though they interchanged with the Sennheiser tips, so I was at last able to get a seal), and the cable is very microphonic and annoying if you move.
I will probably sell these or give them to my daughter, who runs a lot of her phones through the washing machine, at some point and always needs new ones, and I probably won't consider an upgrade like an RE0 without hearing it at a meet first...
Just goes to show how our perceptions (and ears) vary!