When I had my Xd with me, I used Kernel Adiutor as a CPu app. SetCPU is fine too. Most CPu apps allow to stablish a frequency on boot, so people just can use 1,4 if they want via cpu app. Kernel Adiutor also allow disable some cpu cores for non demanding apps and save more battery.
Benefits are in the most intensive emus, like mame4droid, bsnes core from retroarch, PPSSPP or reicast or uoyabause.
About a noob using 1,8 ghz, it depends on their needs and how comfotable they feel flashing firmware and that stuff.