The real problem is buy-in and mobile clients that support it. I have another android device here, and the audio is fantastic. The video works decently too; not as clear as 1:1 Jitsi Meet calls on mobile, but better than Jami, which is what else I’ve tried.
The buy-in problem is obvious, you have to other people who want to test with you. I have auto-registration turned off of mine, to keep from being spammed. So I manually register people.
With devices, I think Conversations is the only one on Android that supports calling. I don’t know of a desktop client that does (Gajim can, but it has some requirements for software that I couldn’t meet). The other issue is: if I text/send files, it works like SMS. But there are in-device settings that prevent inbound calls from working normally. They will on my phone, but I can’t get my other Android device to allow inbound calls without having the app open, if that makes sense.
I’m trying to find someone with an iPhone so I can test it out.
All that being said, E2EE is very neat. I can see the logs in the server to see who is sending what to whom, but I can’t see the text if OMEMO is on. If you use it unencrypted, you can read the plain text that was sent.