Word Complete feature

In certain applications you can press 'ESC' to bring up a list of words that begin with whatever word directly is to the left of your cursor. I say directly as it will auto-complete if there is only one option.

Anyway...how many of you guys knew this existed? The implementation is a little poor, and you can't exactly use it in many app's (safari included), but it's mildly handy when you need to spell a long word.

I couldn't be bothered taking a screenshot, so clicky here [daringfireball.net] for someone else's description.

Ah, what the heck, have a screenshot: