"Not as efficient as it used to be, but definitely worth trying for anyone using a lot of addons"
-The World of Warcrafters
(Click HERE for more information)
What does it do?
Zoom!!! makes your UI load faster by preventing garbage collection during the UI load cycle.
In particular, it fixes bad behavior incurred by Rock addons, but it'll benefit you even if you don't run Rock mods, as well.
This won't work if you're on a FAT32 filesystem (Windows 95, Windows ME, badly configured Windows 2000/XP). Also, if you don't run many mods, you likely won't see a huge benefit from this. The more mods you run, the more benefit you should see.