People on the net did many performance testing on Erlang, and it shows that Erlang clearly wins over other environments. And I see that more people are experimenting with it and there are real systems built on it, and performs incredibly. The language is not easy to learn for someone (like myself) who worked in C++ and Java for many years and only touched Prolog (and Lisp) very lightly. It's very fun to play around with it, but it'll take a while for me to be proficient enough to write a big application in it. I was a bit bored with Java and was looking for something new, so it's alright.
I started wondering why this (Erlang way of concurrency) can't be done in Java, and found something: Kilim. (and Scala's concurrency.) It is too early for me to say anything about them as I don't know enough, but it's worth reading a few pages. This page shows Java+Kilim out performs Erlang: http://stephan.reposita.org/archives/2008/06/22/erlang-vs-java-benchmarking-update/
Here is a posting about Erlang and Scala: http://yarivsblog.com/articles/2008/05/18/erlang-vs-scala/ I only read and played around basics with Scala and thought it's just a way to add FP to Java. After reading above posting, I looked at Scala site and found this article: http://www.scala-lang.org/node/242. Take a look at the example code. It's very similar to Erlang how concurrency is done.