I have updated from Sierra to High Sierra and prior to that from Yosemite to El Capitan. I have had no problems whatsoever with any of the upgrades at all.
There have now been four updates to High Sierra so I think it is now reasonable to assume that it is safe.
Is it worth it? Well I have found the upgrade to be worth it but a lot depends on your needs and the other software you use.
My view, for what it is worth, is that if your device is capable of being upgraded without any ill effects then I can see no reason why not to.