If your goal is to build robust, mature web services the Java (Java and the friendly neighbours Scala and Clojure) and .NET (C# and the friendly neighbour F#) e

If your goal is to build robust, mature web services the Java (Java and the friendly neighbours Scala and Clojure) and .NET (C# and the friendly neighbour F#) ecosystems are very hard to beat. Hell, if you're choosing the latter get yourself an Azure description, build a new Mobile Services host and off you go -- Everything you would ever want is included out of the box (including client to server datasync), you only need to figure out what storage and other services you want to use (e.g. Microsoft's PN service for easy crossplatform notifications) and bring along your business logic.