So one of the annoying things I noticed was that tab autocompletion for zsh was broken if I was using it with svn; showing:
_arguments:comparguments:303: invalid argument: ARG
Based on notes here I fixed it by doing the following:
$ cd /usr/share/zsh/4.3.4/functions/Completion/Unix/_subversion
$ pfexec mv _subversion ~/original._subversion
$ pfexec wget http://gvn.googlecode.com/svn/trunk/contrib/zsh/_subversion
$ pfexec chmod 444 _subversion
It all works now :)