If you have not used a spinner before then I would suggest that you first use something that require more human imput like The Best Spinner or Spinner Chief in order to understand the basic principles. However if you must go fully auto then I would suggest you go for Wicked Article Creator. I have it and understand it is similar to wordAI but a one off fee of $47.
There are a wide range of applications that might benefit from the content rewriting capabilities of ArticleRewriterTool. The obvious applications include building content for your website or blog. Other applications include any kind of essay or creative writing (virtual or not), twitter, newsfeeds, Craigslist posts or even paid article writing services.