Pros: Price / Performance, Customer Service, Sound Quality
Cons: Custom fit - Excellent when it fits, an effort to get there
The quads sound fantastic to me. They are my preferred sound signature - all the detail, very present bass, but honestly not fatiguing or overpowering, very slightly attenuated treble. All this leads to a detailed yet warm sound, and the slight roll off on the treble keeps them from being fatiguing. These are concieved as a stage monitor first, and as a high end pair of headphones for musical enjoyment second, which always works well for me. So many "audiophile" headphones have some sort of built in "wow" factor somewhere in the frequency band that eventually makes them fatiguing to me. The accentuated bass comes closest to this in these headphones, but stops short of being fatiguing. It lends the sense of warmth that I enjoy. A great set of headphones (ok, iems), and a nice first (and very possibly last - they are that good) foray into custom iems.
Fit was perfect in the right ear, questionable in the left. After 6 months of intermittent use (headphones suit most of my listening better, but iem's fit a need for traveling and privacy) I have finally sent them back for a refit on the left. I'll try and remember to update when they get back.
Note that 1964 Ears has always - without exception - been gracious, courteous and just plain awesome in customer service. Heck, they ponied up for overnight shipping, and bent over backward to complete these for my birthday this year! Aleksey even hand wrote a happy birthday note to me, and stuck in an iTunes gift card! Seriously nice folks.
There are a lot of custom iem options out there, and it is hard to choose. I am very satisfied with these!