My MTB has them but I've been riding it for 13 years and thousands of miles, I'm so in tune with it, I probably don't need them.
I don't have them on my road bike and I'm still getting used to it.
I really want them on the tandem, because if you look between your feet all you see is the timing chain.
On my two C&V bikes the lever is a good enough indicator.
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Genesis 49:16-17