While it's not bad, it's not that great a universal tool either. My native language makes use of a lot of compound words and Google's spell checker often gets confused when I combine words according to the standard grammar.

I can see and understand the technical limitations, but tools like Microsoft Word seem to do a much better job than Google's spell checker, even in things like Google Docs.

Google search will often suggest splitting up words and sometimes even does it transparently, which can give entirely wrong results because suddenly Google matches words across a sentence instead of specific compound words. It's kind of frustrating to have to resort to quotation marks for some single-word search terms.

I get the feeling Google's spell checker doesn't check spelling, it just tweaks the input until it manages to find more results. Not quite the same, because a lot of "fixes" often have entirely different meanings in my experience.