Never settle for using a spell checker. When writing you need to take the time to manually edit your work for spelling, grammar, and mechanics. By using only a spell checker you are setting yourself up for mistakes. Spell checkers miss homonyms like to, too, and two. Spell checkers are not helpful if you spell the word incorrectly but it can be a correct word in a different sentence. For example, if you write, I lived the new jeans that I bought at the mall, the spell checker will not recognize that lived is not the right word for this sentence because it is another word that is spelled correctly.
Spell checkers give you the advantage of being able to catch obvious misspellings and typical grammar errors. It is one helpful tool but it should not be the only way that you edit your writing work. Take the time to do a proper edit and your writing will be much more effective.