Hi,

there are two rather new "add-ons" to ess that -- when activated --
break the connection between the org document and a R-src-buffer:
auto-complete-mode for R:
http://www.emacswiki.org/emacs/AutoCompleteSources#toc2
yasnippet for R: http://www.svenhartenstein.de/Software/R-autoyas

As especially the latter seems really useful, I want to ask, whether
somebody has an idea of how to get them work in org-mode.

Regards,
Andreas