title: elpa + ESS + auto-complete works only partially
body: <p>in an Emacs-loving rampage I installed a bunch of packages via elpa (MELPA/marmalade). <a href="http://www.emacswiki.org/emacs/ESSAuto-complete" rel="nofollow">Here</a> 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).</p>
  
  <p>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. <code>(setq ess-use-auto-complete t)</code> as suggested somewhere) but no hope.</p>
  
  <p>I'm using Emacs 24.3 on OSX (shouldn't make much difference) and a recent ESS (13.09); my .emacs merely <code>require</code>s ESS and AC (plus <code>(ac-config-default)</code>).</p>