The great thing of Google tools is that they are useful. Not only useful but they have a knack of taking something that everybody does and then add something to it that makes it better. Gmail was great; all the mail that you receive online AND presented in a way that makes sense.
When you receive as much mail as I do, most of it overwhelmingly from the same "source", mailinglists. Many people are subscribed to the same mailinglists and the reason why most people use Gmail... It would be cool if it were possible to identify mail addresses like the WMF mailing lists the point is that they can be stored differently. The content is not personal and it would be nice if it could be treated differently, it would be nice if mailing lists could be identified and stored separately.
The great news today is the new chat functionality that was added today. People who do not use skype or IRC but who have Gmail now can be chatted with. Two people I have communicated with for quite some time, now are available for a chat.. really powerful and guess what, one of them uses Google talk.. That was really sweet.