Minor annoyances after trying it out for a few minutes: 1) The app requires you to sign up for conversations longer than 5 exchanges. 2) It disables my keyboard's word suggestions and instead forces its own – English – word suggestions upon me, making it very hard to write in e.g. Spanish. 3) Even typing in English is weirdly difficult – there is some lag and no autocorrection. 4) The text-to-speech and speech-to-text algorithm only supports English.

But hey, better than nothing.