Mac OS X Hints yesterday published this hint regarding a nice little feature in TextEdit: word autocompletion.
Not only is the feature well documented, but it isn’t new either. Look at this picture:
This is from the TextEdit Help Viewer… under Mac OS X 10.4 Tiger. But it’s probably even older (I’d check on my blueberry clamshell iBook G3 with Panther, but it’s doing stuff under Mac OS 9 at the moment). Note that the autocomplete shortcut can also be just the Esc key (Option-Esc works just fine). And the feature isn’t even hidden, there’s also a command in the Edit menu.
Edited to add: I should clarify that this autocomplete feature is not limited to TextEdit, but it’s a system-wide service, and thus works in other Mac OS X applications as well, like Mail.