+1 to your decision. I HATE site that use usernames instead of emails... i wont even use sites that do that unless i really really have to (like my health care provider).
The problem is not displaying a username. The problem is using the username to login. Because users forget that.
If you're stupidly using your email as your username then your email becomes public should the site you're on show, at any point, your username.
Which is why sites correctly done use the email for login but display a username and never your email. Correctly done sites also forbid username from containing '@', so that you can be sure that people don't do anything retardedly stupid like using their email as username, which would be displayed publicly on the site...
