I rate the B-screw as right up there with the ability to tweak the brake pad toe-in and front derailleur cage angle and shape. (Though, many front derailleurs are no longer "tweakable" with a crescent wrench like the old plate steel cages of the 1970s.) In a perfect world. none of these are needed, In the world I live in, these tweaks often turn my bikes from ridable to quiet joys.

Ben