Latency isn’t that much of an issue. There might be greylisting for the initial message, but once the receiving server knows you, it’s pretty usable. And since everything is an email, you can “chat” with people that don’t use DeltaChat and they can reply using their normal email program. If you’re not using encryption, that is.

I do like that last part. Still, it would be difficult to have a contemporaneous conversation that way.