For me:
1. Housing termination and ferrule capping. If that isn't done right - ALL brakes will feel like and perform like crap!
2. Solid reliable stainless steel cables that don't fray easily nor break easily at the lever ends.
3. Pads that are a tad on the soft side that don't fade too much under heavy use or muck exposure.
4. Even the cheapest calipers and bolts can do a decent job - i.e., if my Campy's failed and I was told to live with some Tektros for a week - I wouldn't exactly have a mental breakdown. I'll live...
=8-)
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5000+ wheels built since 1984...
Disclaimer:
1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:
Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life