I come from a long line of mid-range earphones including the Sennhiser CX300II, Klipsch Image S4, Monster Beats by dr dre Tour, and Monster Jamz. I was looking for an earphone that I can continue producing electronic music on and concluded, by the reviews, that the Yamahas were my best bet. They were not that expensive here in S. Korea, being approximately 124 dollars. I craved prominent bass (not basshead-ish nor Balanced Armanture like; just clear bass), good instrument separation, and good build quality.

First Impressions:
When I first put these in and listened to Below Us by Seven Lions, I was amazed at how clear the bass  rumbles and kick punches me. The mids really bring out the 'bodies' of the bass and warm instruments. The only thing that caught me a little off guard was the treble. The treble felt like it had a high speed lfo (low frequency oscillator) attached to it, giving it a fast, fluctuating, vibrato like tone, strange. These are not-suprisingly tuned a lot like at type of studio monitors that Yamaha makes: the HS80Ms. This is ideal as I can basically have a portable studio now; I no longer have to worry about mastering issues when I produce music!
 
After 3 days:
After a few days of use, I have now become accustomed to the strange treble and enjoy it. All my music seems to have become smooth. The bass massages me, the mids soothe me, and the rather unique treble gives everything and airy, jazzy feel. I have continued discovering new elements of my music. The soundstage and separation helps this a lot. I find percussion lines and unknown riffs flying here and there in small corners of the headphone. This is very satisfying as I need to be able to hear all the details in my music. The Klipsch Image S4 doesn't hold a stick to these Yamahas as the Klipsch have very low volume levels. The Klipsch would seem more geared towards listening to classic rock music or any other kind of smooth and quiet music. The Yamahas can reproduce anything well except for Classical. The treble seems to be a big factor in preventing the Yamahas ability to reproduce Classical properly. I am not a big fan of Classical and listen and produce mainly Progressive House and Trance, which was not a problem. I expect these to sound even better and have more controlled (stable) bass by the time I reach approximately 100 hours of use. I also expect to be using these for at least 2 years; though I prefer they last me a lifetime.
 
I would recommend these to anyone within the $100 to $150 range budget!
I would recommend you to buy these if you are an audiophile and if you find this for less than $120!
I would recommend these to anyone who listens to and/or produces EDM (Electronic Dance Music)
I would recommend these to anyone who listens to Jazz or Chillout music.
I wouldn't recommend these to bassheads; these have very clear bass and it goes down low, but in terms of quantity, the Monsters earphones have a little more by sacrificing the mids.
I wouldn't recommend these to treble lovers; they might have trouble adjusting to the strange treble.
I wouldn't recommend these to anyone who listens to Classical; try the Sennhiser IE8/IE80s then, they have a wider soundstage and more 'normal' treble.