First, thanks for this plugin. It is really useful.
Second, if you want to add more variables and customize your "new user emails", follow this (referring to version 0.5.1 of the plugin!):
e.g.: add the user's first name to the email:
1. insert a new line after line 347 (without quotes): "$user_first = stripslashes($user->first_name);"
2. In line 350: after the useremail variable add (without the quotes) ", '/%userfirstname%/i'"
3. In line 351: after $user_email, add (without the quotes) ", $user_first"
4. Click on update file...
5. Go to the user email settings screen and add your new variable: %userfirstname% in your desired location.
1. if you need the user's last name, use: stripslashes($user->last_name)