I have now had UM Miracle for more than three years and still find it an excellent CIEM. In terms of frequency response, I think it is VERY balanced, especially compared to full size headphones like HD800 (way too bright) and LCD-3 (way too dark) and also LCD-2 r2 (too dark) and the unmodded HE-6 (too light). In fact, to my ears the Miracle is the most balanced and correct in terms of tonality of all these high end headphones.
There are only two areas where I find the Miracle's frequency response to deviate from correct: Sub bass seems to have a bit too much quantity. However, I actually like this. The output in the lower treble is a bit too little, which means that classical and choir music isn't sounding as open as it should. Female voices in general should suffer from this too, but for some reason it usually isn't prominent. I guess that it's because the dip isn't in the upper mids, but in the lower treble.
So - in short - I find UM Miracle a stellar performer in just about all genres except classical and choir music.
4+ years and remains one of our favorite IEMs.