Well, moving away from SMS doesn't mean you're stuck with just Signal of course... what about XMPP for example?
I consider Signal an imperfect but extremely useful option for a very specific use case: getting my family and friends to send me (and each other hopefully) encrypted messages, just cause.
And after having done that, I can say I see the genius of the approach Signal has taken.
XMPP is looking better these days than it did not long ago. OMEMO makes encrypted messaging a lot simpler, Conversations provides a reasonable mobile client, and Prosody makes deploying your own server easy. Still a ways to go on some things (push notifications), but a lot better than it used to be.
