It's very good. The voices reminds me of speech from real life people with accents. It's good enough for voice overs where previously real-life voices would be too expensive. I would say that it's better than Amazon's Polly when it's used to read long passages of text.
I don't know. They're good but they still sound robotic. For me, they work for applications where I sort of expect/accept that I'll get computer-generated speech anyway. But I wouldn't use them as a general substitute for a human speaking, even someone like me who doesn't exactly have a radio voice.