I'm finding two things which are perplexing:
Entered usernames cant contain any capital letters? It says it must be alphanumeric if you try.
I'd like to have it say (Must be all lowercase) beside the 'Username:' label... Or accept capitals and sanitize them upon registering...
When a user enters a custom password (using the password custom field type). It e-mails them that password/confirmation, then when they are approved-- it sends them a new random one. For now I've removed the custom password, and that works, but then they have to change it after, which is a bit clunky.