In turn, you can focus your development effort on new systems, new features, and scaling existing infrastructure since you are not bogged down in maintenance mode. Even better, you can often postpone errors in a system which are non-fatal. I often wait until I have a couple of bugs in a system and then I'll work on that system for a few days fixing them all. In systems where even the smallest amount of brittleness destroys them, this isn't really an option.

Another experience of mine is that Erlang systems tend to take a bit longer to write compared to cranking out a fast solution in another language. But the payoff is that your Erlang solution tend to have better robustness as load increases and people start using the system.

The community is small however, so you'll need to write more code yourself in-house as a result. For some problem spaces, this will hurt a lot because there are off-the-shelf solutions in other languages. On the other hand, larger projects which are more specialized can benefit from you knowing your own code better.