Notifies administrator (site_mail) of new user registrations. Starting with Version 1.2 you can now define both the address it goes to and the subject and messages emailed. Starting with 1.8 you can get emails when someone updates there profile as well.
Version 1.2 has a bug in the profile code. Please upgrade to the latest version. When upgrading from 1.2. Please going into admin/settings/register_notify and reset to default.
Issues
As with all contributed modules, when considering submitting an issue: