Used paid version for 3 months. While this plugin is very user friendly and support is awesome – I was not able to achieve getting any noticeable new traffic from search from other languages. The main issue is that translation is made on the fly “by design”. It looks like translation in Chrome, when firstly you see the original content and as page loads – it becomes translated.
When Google crawl the page – it see content in original lang and mark it as duplicate. As result – were few pages indexed as original translated content and no organic traffic to it.
Conclusion: if you need just a way for your visitors to switch lang – it may be ok. Even if the translation quality is just as any machine translation – it may be useful.
But don’t expect to get any new search traffic by using it even in paid version – proceed with human translation from the beginning.