Google gave us a hint of Gmail's new look with a preview earlier this year, and it's now finally begun to roll out the real thing. Sometime over the next few days you should see a "switch to the new look" link in the bottom right corner of Gmail which, if clicked, will open up a range of new features and design changes. Those include a streamlined conversation view (complete with profile pictures), three different density settings (plus "elastic density" based on your display), a new batch of high resolution themes, improved search, and a refined navigation panel. Head on past the break for a quick video detailing the changes.
Update: Well, it looks like those "few days" turned into just a few hours. Google's now confirmed that the new look is available to everyone.