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.
__________________
Genesis 49:16-17
"Well, well!" said Holmes, impatiently. "A good cyclist does not need a high road. The moor is intersected with paths and the moon is at the full."