Good topic though I'm not sure it's all that revolutionary as many seem to say. If you read those humongous threads on Livewires, FreQs, or UE10/11s with an objective viewpoint you see a very clear picture:
Some people find their customs the greatest thing since oxygen. These people write at length about how fantastic they are, about how wonderful they feel compared to universals, about how it's the greatest audio purchase they ever made. The rest of the people, those that actually own them, are posting about how they're sending in their customs for the Nth refit after spending a week carefully adding nail polish to determine where and how it needs built up or some analogous fit/sound issue. Some of those rest wind up returning them, a few wind up on the custom pep squad, and most seem to reach a point of "well, this seems good enough" and move on to other things neither very disappointed nor very pleased.
I became very infatuated with the idea of customs last winter after beginning to believe I wasn't going to find a universal to suit me. After I read all those threads, at first merely seeking info on which custom to go with, I realised that they weren't necessarily a fix for my problems. Once I realised I could wear UE's super.fi 5 well enough I decided it was between Livewires and TF10s, and after even more reading of tales of refits and settling on "good enoughs" for custom fits, I opted for the TF10 (which got swapped for SA6, but that's a whole other matter
).
It is a good topic, but it is stating what really should be obvious for those who do their homework: customs are for when you're willing to invest the
time and
money into seeking that ultimate fit IEM, not when you're simply seeking a good IEM. If you find a universal you're happy with for both SQ and fit, it seems unlikely going custom is going to net you anything but bragging rights.