SpinnerChief works in a similar way by polling its huge Cloud Thesaurus for the statistically best synonym. As the Cloud Thesaurus grows, so it gets better and better at synonym replacement. The cloud thesaurus supports more than 20 languages, including German, French, Spanish, Italian, Swedish and Portuguese (both Brazil and Portugal), Dutch, Indonesian, Greek, etc...
Google is getting VERY good at catching spun content so you'd better be talented at manual spins. If they DO catch you, of course they'll spank you... and hard. So anything you use spun content on is inherently AT RISK. Worse yet... Google gets better at finding spun/poor content every year. So in the longrun you're screwed. I'd weight your other options and see if you couldn't find a cheaper source for manually hand written content.
A website with lots of unique and human-readable content is going to give you the best ROI. The more quality readable content your website has, the more exposure it will get from major search engines such as Google & Yahoo. But creating unique content takes time as you first need to develop content creation strategies and then you need some hours to write a full SEO optimized content. How great it would be if you can produce quality content within minutes! Yes, it's possible with the help of this free Article Rewriter Tool developed by SeoToolStation.