I am the site administrator
I misspelled my name (*first name)
I clicked on my profile and selected "edit profile"
I corrected the spelling of my name (left all other options unedited) and clicked "update profile"

I get the following error:
"Only lowercase letters allowed
More information about this error"

Click on "more information" the screen says
"error/moodle/usernamelowercase
There is currently no text in this page. You can search for this page title in other pages."

I go back to the profile and attempt to change my username from "Admin" to "admin" I get the following error:

"This username already exists, choose another"

There is only ONE user – at this point that is me, the site administrator. So there is an error in the user name because of the capital "A" and yet, it cannot be changed because the username "admin" already exists.

Is Moodle 2.7 REALLY ready to use?
It seems to be rife with errors and circumlocution errors that have no solution (in this case aside from using my PHP admin to edit the database, which isn't user-friendly)