I was recently on a panel discussion that was asked why should a developer should bother to learn Groovy. They cited Dice.com job results. Much like this blog entry.
Trendy Bastards, Aren't We?
My response to the question "Why should I learn any new technology" is this... do you want to wait to be one of the cogs in the machine? Just another developer among hundreds with a buzzword compliant resume? Or do you want to be the person who learned the new tech, like Groovy and Grails, ahead of the curve, and was then in huge demand while the rest of the industry plays catch up? Do you want to be the person who knows the new, cutting-edge tools and introduces them at work? Or do you want to work with what someone else chooses?
Don't get me wrong... I love Ruby and Rails. I've done very little with Groovy and Grails. But if you limit your learning to existing projects, that means you're limiting your role within your company, and limiting your career, to following the crowd. It's hard to catch a wave after it's crested.
Will every technology you learn be a home run? No. It's like buying stocks. Some will be a home run, some will be a solid return... others will be a learning experience where it's a complete loss.
But over time, if you invest regularly in your knowledge portfolio (or your retirement account), you'll always end up with a decent return and be very comfortable.