Beyond the Actor model in erlang, it's got lots of neat tid-bits, especially when you start working with OTP. You can actually have a pool of generic servers waiting to be transformed to any type of server you may happen to need at any one moment. I found that to be an odd thing at first, as it sounds like an invitation to a 'server pool manager', and all its hassles. But neat nonetheless.
I'm a big Erlang fan, but I think that the concepts it introduces can be ported to other languages with enough work. Bringing Erlang concepts to more traditional languages has the potential to completely transform how we think about structuring massively parallel programs. Personally, I can't wait for python to transparently scale to thousands of machines. A pipe dream, perhaps, but that's what I'm pulling for.
I have no problem using Erlang when I need it, but eventually concurrency is a problem that every language is going to have to deal with more effectively than it does now. The Actor pattern makes a lot of sense to me conceptually, and makes it trivial to parallelize systems. It's not like Erlang's the end all, be all of programming languages, but it is a forward looking one. I look forward to other languages catching up with it.
