[mindcrime]

Btw, why Groovy on Grails ? Any specific reason ?

No, that was me doing what I said everybody would do - recommending my personal pet favorite. :-) I just happen to really like Grails as a framework for developing web-apps and Groovy as a language. The combo hits a "sweet spot" for me in terms of productivity and ease of use, and leverages a lot of pre-existing knowledge of the Java / JVM ecosystem that I already had.

From a pure "market demand" standpoint, my guess is that RoR or even Node is going to be more valuable than Grails, but I haven't empirically validated that - it's just a hunch. In my case, I'm using Grails in the context of a startup I founded, so it doesn't matter to me what the market is screaming for - it just matters what I can use to Get Shit Done. :-)