These babys will give you everthing you need from an high and IEM. Very strong bass presence, realistic and detailed mids, and non fatiguing smooth, detailed treble. 
 
I think they are the final step before the customs, and if you think about their isolation, maybe you don't need a custom IEM if you have these. These IEM's are one of the greatest solutions for those who don't want to be involved in a CIEM process, but want a great isolation and sound quality.
 
I owned GR07, Westone 3, Westone 4R, Westone Um Pro 30 before these. And I can clearly say that those IEM's are cannot be compared to these monsters. Period.
 
Maybe Shure SE846 can compete with these, which I didn't have a chance to listen. I'm just guessing. 
 
Get these IEM's if you have the budget. You won't be disappointed. It deserves every dollar you pay for.

I was blown away by sound quality of these when I first listened. Yes, these are one of the great universals, but after some time I noticed their flaws day by day.
 
The bass is weak and unnatural, sound is sibilant with FiiO X5. Some instruments are not in natural tone.
 
Everything else was great (especially mids and treble) but those flaws led me to selling them.
 
Comfort is great and isolation is enough for a Universal IEM.
 
Definitely one of the best, but not outstanding.

These earphones are quite big, so if your ears are really small, you can face some problems. Comfort is not great either. Finding a good fit is a little challenging. Don't expect Westone like ergonomics. The cable is good I haven't seen microphonics so far. It has a detachable cable. Overall, it is a good durable product. But comfort and isolation is not great.
 
The Sound: These have dual drivers. For the price you pay, the sound is really good! These have powerful bass response but not overwhelming the other frequencies. And mids, yeah, where these earphones shine. Vocals are clear and warm, enstrument seperation is fine for the price. Mids are taking the front line of the sound. Treble is not sibilant by any means. But don't expect airy treble like top of the line flagship IEM's. Detail level is good, especially when you consider the price.
 
I used Shure SE215's and Westone UM1's. And I think these are the best sounding of the three. And the cheapest!
 
But Shure's and Westone's, comfort and isolation wise, are clearly better then IM50.
 
For 70$, I can't think any better IEM's than these.

Great product from Fiio. I think its really good for starters. Works fine with almost all headphones. EQ is great. Clean sounding. Performance/Price ratio is definitely good. You can't go wrong. And also it can be used as a headphone amplifier alone. Portable. Extras are good.