I expect within a few years that the server side programming landscape will look very different and Javascript will be extremely popular. That's just my personal opinion.
But what about in the here and now, is Javascript a valid choice of server side language or are the various APIs still too immature? Ie. lacking functionality compared to existing solutions in other languages, and too fast-changing so that they make for an unstable platform? Are the tooling options available up there with tooling options for Java, etc...?