I didn't add/create an SSH key when I created my droplet. I received my root password, but I have no idea what user I'm supposed to login as. I used the Ubuntu 11 (64-bit) image.
You are allowed to login directly as root and then create any users that you like.
You get full root access to the droplets.
We would recommend locking down direct root logins after you have created another user and added him to the wheel group so that he can sudo / su.
You won't be notified about changes to this idea.