My oldest was in the vanguard of phonics in our local schools in the UK. His spelling is terrible because he spells things phonetically, which simply doesn't work in English.
Word's little red underline dramatically improved my spelling. Words that I would habitually misspell would annoy me with that little red underline. I'd concentrate on the word and the correct spelling and eventually I stopped misspelling it.
My favorite example... their... almost always I'd write "thier" (the few times I'd write "their" I'd doubt myself and switch it to "thier"). Nowadays I almost never misspell it (it also helps me sometimes to think "the IR").
Without Word's instant spell checking I'd still be a bad speller who'd spend too long running the spellchecker.
