Comment by sam-cop-vimes

I'll try and answer this.

Expressiveness: I could express a solution to a problem with very few lines of code and without the clutter of housekeeping operations like memory management.

Recursion: Erlang properly introduced me to recursion whereas I hadn't encountered it before. This is again related to expressiveness. There is something strangely beautiful about seeing a problem solved using recursion elegantly.

Message passing: when I was trying to figure out how Microsoft's C++ socket classes were implemented and I dug into the code, it turned out there was a hidden window for every socket created and messages were being passed to/from it, but message passing wasn't available anywhere in Visual C++ as a first class construct (at least as far as I remember it). I was overjoyed when I discovered that message passing was a first class citizen in Erlang and how much easier it was to implement concurrent programs than using native threads in C++.

Compared to OO programming in C++ where I was never sure whether I was using inheritance correctly, whether I needed inheritance at all, memory management, difficulty with threads, writing code in Erlang was a breeze.

And the whole support for distributed programming, hot code loading, list comprehensions! I fell in love again with Erlang when I discovered list comprehensions. Man, I could go on.