What would be the best language/library choice for writing a scalable webservice server?
I've been engaged in a project to write a game dissemination and service platform, which would enable game developers to easily outsource game distribution and updates as well as offering certain parts of multiplayer/community such as achievements, rankings, friends and such as a webservice in form of either SOAP or REST API.

I'm not sure how viable it is in terms of attaining market share, but none the less the application should be written as to scale horizontally well in order to absorb any quantity of possible users. Since the project is still in it's early stages I have some degree of influence regarding the language and technologies to be used.

So far my research has narrowed the choice down to either Erlang or a JVM based language.  
Erlang is widely known for it's focus on scalable and fault-tolerant distributed applications and proven track record, but on the other hand it's library ecosystem is nowhere as rich as JVM's.
JVM languages on the other hand enjoy a big community with a multitude libraries, many of which strive to provide for distributed and reliable services, such as Terracota or Akka (which seems to be inspired by Erlang, though I'm not sure how much of it's strength it approaches and would like to hear about it).  
Since language productivity is of equal importance as platform strength and reliability I would lean towards Scala or Clojure over Java if I were to use JVM.
Of course if you think there is another language (JVM or non-) better suited to such a task I'm interested to hear about it.

I wouldn't like to read a bulletpoint list of language's cool features as that's what I can google by myself, I'd rather be interested in your own experiences with writing such an application (a bit in the vein of those blogposts - [link](http://www.metabrew.com/article/a-million-user-comet-application-with-mochiweb-part-1)), though not only concerning raw performance but also language and library issues.

I would like to hear what your (or your company's) language and technology choices for such a type of project were, what motivated such a choice, what your experiences using the chosen platform were and did it ultimately deliver.  
All insight will be greatly appreciated ; )
What would be the best language/library choice for writing a scalable webservice server?
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I've been engaged in a project to write a game dissemination and service platform, which would enable game developers to easily outsource game distribution and updates as well as offering certain parts of multiplayer/community such as achievements, rankings, friends and such as a webservice in form of either SOAP or REST API.

I'm not sure how viable it is in terms of attaining market share, but none the less the application should be written as to scale horizontally well in order to absorb any quantity of possible users. Since the project is still in it's early stages I have some degree of influence regarding the language and technologies to be used.

So far my research has narrowed the choice down to either Erlang or a JVM based language.  
Erlang is widely known for it's focus on scalable and fault-tolerant distributed applications and proven track record, but on the other hand it's library ecosystem is nowhere as rich as JVM's.
JVM languages on the other hand enjoy a big community with a multitude libraries, many of which strive to provide for distributed and reliable services, such as Terracota or Akka (which seems to be inspired by Erlang, though I'm not sure how much of it's strength it approaches and would like to hear about it).  
Since language productivity is of equal importance as platform strength and reliability I would lean towards Scala or Clojure over Java if I were to use JVM.
Of course if you think there is another language (JVM or non-) better suited to such a task I'm interested to hear about it.

I wouldn't like to read a bulletpoint list of language's cool features as that's what I can google by myself, I'd rather be interested in your own experiences with writing such an application (a bit in the vein of those blogposts - [link](http://www.metabrew.com/article/a-million-user-comet-application-with-mochiweb-part-1)), though not only concerning raw performance but also language and library issues.

I would like to hear what your (or your company's) language and technology choices for such a type of project were, what motivated such a choice, what your experiences using the chosen platform were and did it ultimately deliver.  
All insight will be greatly appreciated ; )