I use Emacs with Alchemist [1] and I love it. The integration of common tasks like module reloading, testing and inline evaluation have all increased my productivity when writing Elixir. Code completion, Phoenix support and the ability to quickly jump to function definitions within a project are all nice features as well.

[1] https://github.com/tonini/alchemist.el

Atom has recently gained a significantly better support with the atom-elixir package. Adding language-elixir and linter-elixir packages creates a moderately enjoyable experience.

I'm currently using Atom with this package: https://github.com/msaraiva/atom-elixir

Depends on what you're used to. Certainly you get the normal bits that editors all support: text coloring, autocomplete + basic code complete stuff + whatever linter people have created. Not resharper or heavyweight sorts of IDE things yet.

I never had any issues here with sublime

Alchemist for Emacs is truly wonderful.

You really want to try Spacemacs (emacs with layers) with Alchemist

I use MacVim + the Janus extensions[1] and it's great. I hear good things from people using Atom and Sublime too.

[1] https://github.com/carlhuda/janus

It's rubbish, but the IntelliJ plugin is improving at a rate of knots:

https://github.com/KronicDeth/intellij-elixir