Very clear message. We’ve been doing this almost from day 1. Every invoice a user receives, has the message: help your entrepreneur friend out, tell him about the software you’re using and earn €. It’s a great impulse and also a great reward to your ambassadors (users) who spread the word.
We don’t give the new user a warm welcome with a discount. Something you thought about why ‘reward’ a new user as well? Does it increase the sign ups?
PS: After reading for years, and never responding, I felt the urge to do it this time :).