I get less irritated about a person misspelling a word because sometimes it depends on where they grew up and what dialect they use. The one that bothers me more than anything is when someone says neither instead of either, like you can put this on neither side of the bed instead of either. I was taught growing up that neither meant "not" not you can have your choice but to day you hear it on TV all of the time, especially on decorating shows.
The other thing is I hate to have misspelled words in a book that I paid good money for. They should have the books proof read before publishing them.
I do try to use the spell check when ever I can.