[couchand]

The first three complaints addressed are far too common for how ridiculous and unfounded they are, and it's nice to see them addressed head-on.

The fourth is simply confusing. If you're not sharing code between the client and the server, you're missing something big (though he does say it might just be the projects he's on).

Modern business software is faced with two competing forces: bulletproof integrity and responsive interaction. Making your application bulletproof requires that business rules are evaluated on the server, but making it responsive requires those same rules to be evaluated on the client. Think about credit card validation: it's infuriating to wait for a round-trip to the server just to discover you've mistyped your number, but that doesn't mean the server can simply trust the client.

At the moment Node.js + browser JavaScript provides the only solution I know which allows you to write your business rules once and only once. Anything else is crufty.

[klibertp]

What about Clojure and ClojureScript? There's also Opa. And Ur/Web, which reached a stable state, based on a growing user base of three use cases ;)

Then there are Seaside inspired frameworks, which generate client JS for the user. There is at least one framework like this for Python and I'm sure there are other for other languages.

JS remains the most well known and supported solution, though.