This is the feature I’m most looking forward to in Lion. Many times a day I go through the process of typing a sentence, seeing the red underline on a word, switching to the mouse, right clicking, selecting the first correct spelling suggestion, moving back to the end of the sentence and continuing. I always wished you could access that contextual menu with just the keyboard but this Lion feature completely eliminates the need.
I wrote that a few months ago, saved it as a draft and didn’t publish for some reason. A month into Lion and I can say that my anticipation was well-founded, I love auto correct in Lion. Adium doesn’t yet support it and it’s hugely frustrating, I don’t know how I lived without it.