Apple in Mac OS X has brought the same error correcting features that exist in iOS for typing to every single text box that is rendered and has a cursor placed in it. This has allowed me to type faster and even if I make mistakes the OS will correct them for me most of the time. It still needs a little bit more time and tuning, but so far it has proven to be absolutely fantastic when typing.

See Preferences -> Language and Text -> Correct Spelling Automatically.