There is a lot of work going on in this space right now and there have been huge advances in the past few years. The neural voices are starting to sound pretty good.

I am working on a product right now that's leveraging text to speech. I am presently using Microsoft and Google TTS because they seem to have models trained in a number of languages.

I'd be curious to hear what others are using, especially in the case where support for a number of languages is required.