Usually Google tests its products and updates internally with its staff before releasing it to the public. With Google Labs, enhancements to Gmail have been released to the public and millions of people can test them and can send feedback direct to the people who created the stuff. I have enabled a few like Signature Tweaks and Superstars. Let us see how it works out. The most popular features will become part of Gmail. I wish Gmail allowed sending of HTML signatures. That is a feature I'd embrace wholeheartedly!
In a first, Google is opening up its testing process by calling on tens of millions of Gmail users to put new features of the service through their paces. Gmail Labs has launched 13 settings for users to play around with and tell engineers directly what they think of them.
The new settings include things like 'Pictures in Chat' which puts portraits in chat sessions, 'Superstars' which lets you put different icons on mail, 'Old Snakey' lets you play the classic game in Gmail, and 'Email Addict' forces you to take a screen break by locking you out of the Gmail for 15 minutes. (More in-depth look into Google workings here)