Companies with telecom products are generally conservative about switching Erlang versions. Most of Corelatus' production systems run R11B-5. Quite a few still run R9C-2. There's no compelling reason to upgrade them, there are thousands of those systems in dozens of countries and most run billing systems. They typically run for years at a time and only get upgraded in conjunction with a larger system upgrade.

It's not like you sit there typical 'apt-get update' a couple of times a day to see if there's anything new you might want...

On the other hand, people who are new to the language generally like to use the very latest because it contains the most features. E.g. later versions have increasingly good SMP support, which may be important if you're working on something which has to scale across many cores, but it's completely irrelevant to me because our hardware only runs Erlang on one core.

My suggestion for a starting point: if you're just developing, follow the R14 sequence, i.e. every time a new one gets release, download it, compile and install from source. If you're ready to deploy now, use R13B04 and let others find the bugs in R14.

Potential biases: I work at Corelatus. I've worked for Ericsson. I maintain the Erlang FAQ.