How does Google feel about misspellings? I mean is a fact that many people search for misspelled things. Does Google have a negative vision about pages including misspellings on purpose or otherwise?
Have you ever used Google before? If you make a spelling error it will correct it and suggest the proper search term. It would be in your best interest to use proper spelling. While you may be able to pick up a couple extra visitors with a word spelled wrong your website loses credibility to the viewers that matter.
If your content is full of bad spelling and grammar it may as well be spun gibberish, no point in cutting corners