There is a difference between adding useful features and adding features. Good services can usually differentiate between the two.

And one more thing, its might go down in history of Gmail due to fact that people may not use it, not just of its quality. Its a new idea and when I heard it, there was a feeling that its really something new as none other Mail providers have this option.

People would know its value only when they are in a situation as said in the blog itself, quoting from it: I, for example, occasionally sign into my Gmail account from a friend’s house when I need to check an important email. Usually I remember to sign out, but every once in a while I wonder if I really did. Now I no longer have to wonder.