Q:

elpa + ESS + auto-complete works only partially

in an Emacs-loving rampage I installed a bunch of packages via elpa (MELPA/marmalade). Here I see that ESS supports advanced AC with a fancy dropdown menu, with documentation etc. out of the box. However I can only use the basic one (e.g. I write "library" once, enter, write "lib", complete).
Is there anything special I have to do? I am no LISP/.emacs genius so maybe I am missing something. I did try some manual flags (e.g. (setq ess-use-auto-complete t) as suggested somewhere) but no hope.
I'm using Emacs 24.3 on OSX (shouldn't make much difference) and a recent ESS (13.09); my .emacs merely requires ESS and AC (plus (ac-config-default)).

A:

Thanks for suggestion, the page on emacswiki does indeed look good.
So I've just installed from elpa as you did. And I didn't get the completion
as you did. But then I did C-c C-b ess-eval-buffer, and the completion
and floating docs are there. And there you go.

