Firstly, Gmail will now work on a variety of screen sizes, resizing itself to fit whatever web browser you’re viewing it on. You can even adjust the density of the views through a simple drop down menu near the top of the page. Emails have been streamlined more to look like conversations, and profile pictures are now included in emails. Themes have been updated to support HD resolutions, searching has been improved, and it’s even easier to create new filters now.
It’s going to take awhile to roll out to everybody, but once you see the “Switch to the new look” link on the bottom right corner of Gmail over the next few days, you can try it out rightaway.