Yeah, I saw this too today while trying to do a transfer. It's so cool and it'll save me the energy of typing an already known username or used username.
It'll also prevent transaction mistake that happens when transferring to people with usernames that can be mistaken - That's if you've already transferred to them before successfully.
That's very true. What a great feature this is going to be for both newbies and oldies alike. Thank you for dropping a comment @enolife.