The slowness of my zsh prompt when in a git-svn managed directory was killing me. I improved it by removing the git status stuff that slows it down...

git_prompt_info.zsh

function git_prompt_info() {
  ref=$(git symbolic-ref HEAD 2> /dev/null) || return
  echo "$ZSH_THEME_GIT_PROMPT_PREFIX${ref#refs/heads/}$ZSH_THEME_GIT_PROMPT_SUFFIX"
}