Auto complete text in Cocoa applications

Here's a tip that some of you may not be aware of. You can use a quick keyboard shortcut to auto complete words in many cocoa applications (like TextEdit, for example). Here's how it works. Create a new document in TextEdit and type the first few letters of a longish word, and then hit Option-Escape. A drop down menu appears of your Mac's best guesses at what you're going to type. Cool, no?

I've only tried it in TextEdit under Tiger, but if you know of other applications that allow for this (as well as earlier versions of Mac OS X), let us know.

Update: Check the comments for a running list of where this is working, and under what version of the OS.  Nice work, everyone!

[Via MacMove]