I ask because my brain really cant absorb too many languages, and I want to make some kind of pseudo-optimal choice. I'm not just talking about some shootout here, but about the the next 5 years outlook.
Am in the same boat. I moved to SF permanently 2 months back, after 15+ years in the east coast. Decided to pick 1 language, immerse myself in it deeply, & then start the interview circuit. The opposite approach would be to pick a bunch of languages ( ruby, python, jquery/coffeescript etc. ) and get a smattering of best practices in everything without knowing anything too deeply. Both approaches have their merit. In SF, I recommend the latter approach - you will find jobs almost instantly if you do that. But still, given my proclivity ( I would rather know everything about 1 thing than something about everything) I chose the former approach. I picked Scala, read every single chapter of Odersky's book, & subjected myself to 19 total interviews at 2 multibillion$ companies using Scala exclusively for a "new project built from scratch".
I got offers at both. Now am debating which one to join.
tl;dr Scala is that pseudo-optimal choice you are looking to make. In SF there are a few very-nice Scala jobs with 6-figure salaries & tons of RSU's thrown in...but only if you can hack it. The questions you will be asked in the interview are definitely esoteric & very academic ( difference between reader monad and writer monad, reverse a list without mutation using a foldLeft, kruskal's algorithm in scala, merging graphs with common edges where each edge is a tuple, etc. ) Its not web apps, its not "software engineering", and its not everybody's cup of tea. But if you like academic CS, Scala will not disappoint you.
I am not in the valley, but it may be that you picked up on some buzz/conversations in general that lean towards scala. It is quite puzzling since Indeed.com's trends shows a massive lean towards Clojure vs Scala.
http://www.indeed.com/jobtrends?q=scala%2C+clojure%2Cjruby&#...
On an absolute term, Scala still leads the pack (http://www.indeed.com/jobanalytics/jobtrends?q=scala%2C+cloj...)
This is maybe a little too obvious if you understand left folding at all. A less trivial exercise in the same vein is to implement right folding via left folding. It's just a one-liner, but if you haven't tried it before, it's enlightening and worth giving a shot.
I am not a fan of the required cognitive overhead that scala takes to get started -- reading someone else's code reminds me a lot of C++ and the tooling still needs to catch up. If any of the JVM languages are going to break out, I'd put my money on scala. JRuby has its place as well, and I know of a few high profile projects done in it, so it wouldn't be a bad choice for consumer apps. For enterprise, I think static typing has some major wins.
I kind of want Scala--, to be honest...
It wasn't right for us on this project, but I can definitely see going back to it for other projects.
If Scala/Haskell/Go would become more mainstream, and had a very straight forward / magic-free 1:1 conversion to javascript, then node.js will have much less appeal to me.
After that, if you want to switch to another JVM language, do it, but you should have a much clearer reason than "I want to use an alternative JVM language". Something about that language should grab you. Personally, I think Groovy's great for perl-type work where you'd like to just clack something out in a terminal rather than starting up a new project in eclipse. Clojure is an actual LISP for real functional programming. Scala (IMO, no offense) is a pile of academic features that sound great in theory. Jruby is ruby.
If Play had all the community and gems that RoR has, it would be a very, very strong framework, and something that the enterprise world would (years from now) adopt more likely than RoR (for all the wrong reasons, but such is life)
Well, the early days of computing had domain specific languages, and I'm afraid we are getting back to that. The days of a one-size-fits-all language are over. Your best bet is to learn the principles and then the syntax differences just aren't that troublesome. The problem is that when you are new to programming, you learn only a small subset of those principles, and then are stumped when it is time to pick up a new language because it may rely on new concepts.
In education, Scheme once occupied the role of being the language in which you could learn and investigate a broad range of principles of computation. However, the perceived need for vocational training seems to have pushed Scheme out of the curriculum.
Today, Haskell is the best choice for this role.