In my experience, this was true also with Google’s version. The first few iterations were great, then went shit. I need only one thing: add diacritics, and fix basic misspellings. Now all of them try to be “smart” even when they should just add a diacritic to an “a”, they suggest me something completely different even when the word which I need is in their dictionary.

Maybe most people need more, but it annoys me greatly that it tries to be more than simple misspell fixer.