Lots of great answers have already been written. But it's a great opportunity to share again one of my favorite talks: «Be Awesome By Being Boring».
TL;DR: use a new technology only if it solves a problem a proven tech didn't solve it, or if it bring a really significant better way to solve it.
The blog post: Be Awesome By Being Boring on New Relic blog,
And the Cascadia Ruby talk (but this isn't specific to Ruby at all!) Cascadia Ruby 2014- Be Awesome By Being Boring youtube.com/watch