First and foremost: Great plugin!
Two errors on a multi-site installation.
But when I from the dashboard first change the admin username and log out I cannot access the change id option. I will reach this page, but not being able to change anything:
* The admin user has been removed.
* A user with id 1 still exists. Click here to change user 1's ID.
And when changing username, I got an error on "wrong character's used" (used one capital letter) and still got logged out. Better information to user needed + don't log out on error.