I tried it with Japanese, and it sounded about as good as in English. Only at one point did it sound unnatural. Japanese two-person conversation uses a lot of backchannelling, that is, semilinguistic sounds made by the listener (aizuchi). At one point, the female voice said very distinctly fumu fumu, which is how such aizuchi might be written in a script or manga. In actual speech, though, it would be a continuous sound without syllables and with a rising and/or falling intonation.
I tried it with Japanese, and it sounded about as good as in English. Only at one point did it sound unnatural. Japanese two-person conversation uses a lot of backchannelling, that is, semilinguistic sounds made by the listener (aizuchi). At one point, the female voice said very distinctly fumu fumu, which is how such aizuchi might be written in a script or manga. In actual speech, though, it would be a continuous sound without syllables and with a rising and/or falling intonation.