Could improve

This app is recommended by Edward Snowden, so I guess its pretty safe to use.

People should stop complaining about giving contacts access. The app was always intended for privacy, not anonymity.

It would be perfect if there was an incognito mode. A way to talk to another user without giving your phone number. Instead of registering phone numbers, giving the option to register an username (like Skype or Wickr).
You can use another phone to receive the SMS registration though.

Another welcomed feature is message timer.

Jstelar about Signal - Private Messenger, v2.3.4