I have been developing with java more than 8 years. I have had implemented many technologies with ejb, spring, struts, hibernate etc.. you name it; I have faced with many technologies in java domain.
It has been few months I have been working with ruby (and ruby on rails). I am surprised how everything is easy to do. I witnessed whoever start programming with Ruby first resisted with some enterprise buzz words but then all ended with same decision: "I will never touch to java". :)
It is really much much easier to achieve what is on your mind with ruby. Once you get used to flexibility of dynamic language; open classes and many other features (once you achieve to change your mindset) it will be very hard for you to go back to java domain.
It is not easy to start a new language; new set of frameworks and you may think that you are throwing away the experience of years with switching to ruby. But calm down; it is fun; do not afraid. You will enjoy it while discovering how it is easy to achieve things. And experience is not lost; it will transform with time.
Of course every language has a place to fit. Java is structural and ruby is a dynamical language. They have both advantages and disadvantages. You can google them. However what I believe is; Ruby is the way to go. It helps me too much to solve problems much more easier. I definitely recommend you to check Ruby; but do not forget; a simple hello world is not enough; you must spend time and a project at least.
Also please check this graph; ratios of languages on github: http://4.bp.blogspot.com/_FsLa1cMTCWU/TGBlqQEs5yI/AAAAAAAAAXM/HkwNFJnohoI/s1600/top_10_github_languages_by_reps.png
Especially Ruby on Rails framework is very successful and I am believe it has a part for Ruby to get popularity. Do not afraid from the change :) http://www.changecycle.com/changecycle.htm
"Because things are the way they are, things will not stay the way they are."