The Gmail Notifier has two functions: the obvious function, which is to tell you when you have a new message in your Gmail Inbox; and to set Gmail as your default email application.

Google Desktop’s Sidebar also tells you when you have a new message in your Gmail Inbox. It does not, however, allow you to set Gmail as your default email application. Since Sidebar provides one half of Notifier’s functionality … why not the other half, too?