The update is available via Software Update, or directly from Apple's site for and . If you don't see the update in Software Update, however, it's probably because your machine doesn't need this fix--it seems the problem only affects certain Macs released in 2009 or late 2008. Here's the list, straight from Apple:

If you don't have such a machine, you don't have any performance problems...at least not the one that this update addresses.

With my hopes dashed for personal improvement courtesy of Performance Update 1.0, I guess it's back to the gym for my personal performance improvements.