GMail is very cute, though I would never use it seriously until it has a supported way to export my email to somewhere else. I keep almost all my email, and I’m not going to put it into a system from which I might never be able to extract it. And that may take a while – they wouldn’t want you reading your mail via IMAP and so avoiding the web-based advertisements.
On the other hand, there are various utilities which do let you interact with it other than simply through the web interface. Here are some for Mac users.