Personally, I think that the default message that is sent to users after they register on a UBB is pretty crappy. Just about half of the people who register on my board email me, asking how to change their password. I know that the default email shows how, but people who aren't familiar with UBB need a litte more instruction.
I would like the ability to create my own email message that would be sent out upon registration. I would also like to be able to change/modify the email via the control panel.