Since the story link is just to the project github page, here's a blog post from the person who did the performance optimization talking a little more about what he did:

http://blog.patshead.com/2011/04/improve-your-oh-my-zsh-star...

Here's the exact pull request for that commit, with quite a bit of discussion about why it's faster and why it was done the "wrong" way before:

https://github.com/robbyrussell/oh-my-zsh/pull/269

Hope that helps anyone else who was curious about exactly what was changed!