If you use a version of Elixir built against the correct OTP release, you'll get the following automatically:

VM Performance improvements - normally this is minor but for this release it's a big big thing

Bug fixes - to standard library and VM

New Erlang APIs to use directly - you can call Erlang functions easily from Elixir, allowing you to leverage new standard library features, but they won't be used by Elixir because of the compatibility guarantees discussed elsewhere here