The more synonyms and phrase relations there are in it, the more the spinner will understand whatever content is thrown at it and the better the content it produces will be. Now that’s not specific to Spin Rewriter but I thought I’d throw in this as most people probably have no idea what a spinner does and then complain when a certain word is replaced with the wrong synonym (context-wise).

Thanks to, search engine dominance can be yours ... for free! The most dependable way to win over major search engines is by loading your site with a continuous flow of unique, readable, useful content. This is why Free-Article-Spinner represents a potential gold mine for you and your search engine marketing efforts. Give your visitors more valuable content to peruse, and give Google more unique readable text to index. It's a win-win situation!

If you think of your content as a pyramid, the broadest coverage of the topic should be listed first. Then move on to more and more specific as you get further into the page. This is useful to your readers, as they can stop reading and move onto something else once you've gotten as specific as they need. And the more useful you are to your readers the more they will want to read your content.
There is also the option to spin capitalized words (assumed to be proper nouns) as well as leave any number of words unchanged, depending on whatever you enter into the "ignore" field, separated by commas. You also have the option to only keep the sentences that were altered a minimum percentage, as indicated by the "Keep Sentences that Changed" option.

Spin Rewriter integrates with almost any SEO software. This allows you to post high quality articles quickly and easily. The only drawback is that you only get something like 300 API requests every 24 hours. You can quickly burn through this if you’re doing multiple campaigns. The developer does not currently offer a plan for heavy API users but maybe they will in the future.