Erlang isn't good fit for every concurrent/parallel application, you may read more about it in my answer on Quora:

http://www.quora.com/Under-what-conditions-needs-would-Erlan...

I disagree with Erlang "deployment hell". The full OTP deployment process is too heavy for anything non Telecom or Embedded. But for regular Internet applications, you just creating self-containing tar.gz file with OTP release using "rebar generate". Then you upgrade your cluster in round-robin manner. There are some open-source tools to automate this process. But it's easy to use any Fabric-style tool or just your own bash/ssh scripts.