prezto [1] is a nice alternative to oh-my-zsh. I find it to be faster and it's more modular.
By the way, one of these days debugging the slow startup time of oh-my-zsh I found the culprit, virtualenvwrapper. Again I didn't have the time to good deep into that, so I just edited out that line from my .zshrc.
EDIT: I'm using urxvt btw
sudo chmod ugo-x /usr/libexec/path_helper