I don’t know any that uses these. On iOS I think the best voice is the Siri voice in system spoken content. The Ivona voices in Voice Dream reader are not bad either.
Just posting a quick “thanks” for the app suggestion. I’m trying to listen to more fiction, and I just started in on the Star Wars: Thrawn trilogy. I hate when the “dramatization” wrecks the quality of professionally-produced ebooks. In this case, characters in the book talking over static-y comms are almost unlistenable for me. They actually try to reproduce the “bad audio over comms” experience for the listener.
This app saved my bacon. Once I mentally re-mapped some of it’s non-standard pronunciations, it turned a garden-variety ePub into a very listenable audiobook. Professional, non-dramatized narration would obviously still be better - but given that doesn’t exist, this app is a lifesaver!