I actually enjoyed the UM2 a lot since it was my first upper end IEM, agree with TCD1975, it is more laid back and very fun to listen to. Ever since upgrading to the Um3x, it was a whole new level, more clarity and balance which i prefer more and matches my music preference compared to the Um2. But the UM2 are definitely bang for buck as a entry IEM.
That's that exact opposite of what I said. The UM2 is more open ... but I've grown to prefer the closed in, but highly detailed, UM3x sound.
If you want a more laid back "fun" sounding IEM the UM2 is a greatchoice (and at a great price) but I peronally prefer the UM3x for it's detail.