When I bought a new dual-sus MTB in 2004, it came fitted with a newfangled "rapid rise" rear derailer. AKA low-normal, it was a Shimano fad, whereby the rear derailer was sprung backward, so that pulling cable would select a higher gear, releasing cable would select a lower gear.
I soon found that I couldn't cope with having two MTBs, both with trigger shifters, shifting opposite directions. I could see benefits in the new shifting concept, so I bit the bullet, drank the kool-aid, and "modernised" my hardtail with a rapid-rise derailer of its own.
I found that I could cope with different types
of shifters operating differently - I had downtube or bar-end shifters on a road bike and grip shift on another commuter, working on conventional derailers... and I could switch to and from them without a problem, and as long as both my trigger-shift MTBs were the same I could operate them without thinking.
Nobody else in the world liked rapid-rise, and the concept was quietly dropped. When I bought a 10-speed MTB 18 months ago, I had to learn conventional shifting all over again, and my beloved rapid-rise XTR derailer went in a spares box. Until about a week ago.
Now I'm learning to think rapid-rise again - this time on my road bike - now resplendent in its XTR derailer. I'm about 100km into the process of re-learning how to shift. It's not quite as well-suited to road riding shift-patterns as it is to MTB , but I think I'm coming to like it again.
It's a rather eccentric beast, my road bike, but I think I loves it... in all its disc-braked, arse-backward-MTB-derailered, wonky-custom-geometried, fat-tyred quirkiness
 the absolute best thing about rapid rise on a MTB is the ability to shift down gears while not pedalling. Bouncing carefully down a technical downhill, you can wiggle your right index finger a bunch of times in preparation for the climb out the other side. While track-standing if necessary. Nothing happens at the time, but when you're able to pedal again, within half a revolution of soft-pedalling the back end will shift from one end of the cassette to the other, ready to start climbing. Compared to a conventional shifter, where to downshift you have to hold pressure on the thumb paddle with your thumb, while turning the pedals over. On a road bike, it's rare to need to dump gears like that while coasting... although it might be good for dropping a couple of gears ready to accelerate out of a sharp corner...