It looks like the creators of Spin Rewriter 9 .0 have really put a lot of work into creating a piece of software that creates readable content. However, Google isn’t stupid and there are a lot of things that can go wrong when you are trying to “manipulate” Google into giving you more traffic. Google hates spam, badly written content and duplicate content. These are all things that Spin Rewriter 9 .0 is capable of creating. You simply can’t trust a piece of software to write content for you in my opinion.
This is absolutely useless. It claims it rewrites English sentences, but it just offers words alternatives, which is only nouns. Also, most of those suggested alternatives are unable to use. If you see their maker's home page, Whitehat Box, you can see numerous people request the refund. It's far from western progressive software like Grammarly or sketch engine. They stole my money with the diceiptive advertisement.
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.
I've ranked websites in the past with spun content, and now they are still on #1 position of google. First year (2014) google found me because my spun was really bad, many paragraphs were just copied and my position drop from #2 to around #20 after a panda update. Later I cleaned all my text with better spun (I didn't buy any article!), my ranking went up again, and with more backlinks I reached #1 and it is still there