Although, Google search suggestions are useful, but they're only displayed if many people search for them. If you type a "long tail" query, Google doesn't show suggestions and can't even finish the words you type.
Google is now reporting of testing an "enhanced version of Google Suggest that autocompletes words."
The new version of Google Suggest autocompletes the word you started to type and guesses that you wanted to use the word "concatenate".
Note: the first screenshot also shows a feature of a Evernote Chrome extension:
[Thanks, Adam, Alex]