The improved time handling is the biggest new feature for most users probably (apart form maps improvements and the new license).
http://learnyousomeerlang.com/time
(BTW, there's also a talk from Erlang Factory by Lukas Larsson on the subject:
https://www.youtube.com/watch?v=gfsc2MyP8p8&list=PLWbHc_FXPo... )