Man, Grails / Groovy never get any love from these poll authors! C'mon, Grails rocks people... :-) Seriously, I switched all of our development from Java/Tapestry/etc. to Groovy/Grails a few years ago, and really couldn't be happier with the decision. Grails isn't flawless, but it mostly "just works" and makes my life SO much easier than before. No, it isn't the "flavor of the day" like node.js or what-have-you, but…
I ditched Grails for Play in 2011, definitely prefer Scala over Groovy any day of the week.
OTOH, I have generally been a fan of languages with static type systems, and I believe Scala tends to be a bit more performant than Groovy. I'll probably revisit Scala at some point, but right now Groovy is working really well for me.